Medical Dictionary A–Z
Clear, easy-to-understand definitions of common medical words and health terms.
A
- Abdomen
- The part of the body between the chest and pelvis containing many digestive and urinary organs.
- Abdominal aortic aneurysm
- A widening of the main artery in the abdomen that can become dangerous if it ruptures.
- Abdominal bloating
- A sensation of fullness or swelling in the abdomen, sometimes associated with gas or digestive disorders.
- Abdominal cavity
- The internal space in the abdomen containing organs such as the stomach, intestines, liver, and spleen.
- Abdominal pain
- Discomfort or pain felt between the chest and pelvis. It can have many causes, from gas to conditions needing urgent care.
- Abdominal ultrasound
- An imaging test using sound waves to examine organs in the abdomen.
- Ablation
- Removal or destruction of tissue, sometimes using heat, cold, electrical energy, or other techniques.
- Abnormal uterine bleeding
- Bleeding from the uterus that differs from usual menstrual patterns in timing, amount, or duration.
- Abscess
- A collection of pus caused most often by an infection, which may form in the skin or deeper tissues.
- ACE inhibitor
- A type of medicine that lowers blood pressure by blocking an enzyme involved in producing angiotensin II.
- Acetaminophen
- A medicine used to reduce pain and fever, also called paracetamol in many countries.
- Achalasia
- A swallowing disorder in which the lower esophageal muscle does not relax properly, making food difficult to pass into the stomach.
- Acid reflux
- The backward flow of stomach contents into the esophagus, sometimes causing heartburn or a sour taste.
- Acidosis
- A disturbance in which body fluids become too acidic because of metabolic or respiratory changes.
- Acne
- A common skin condition in which hair follicles become blocked, causing pimples, blackheads, or inflamed bumps.
- Acoustic neuroma
- A usually benign tumor arising from the nerve involved in hearing and balance, also called vestibular schwannoma.
- Acquired immunity
- Protection against a specific infectious agent that develops after infection or vaccination.
- Acromegaly
- A hormonal disorder caused by excess growth hormone in adulthood, often leading to enlargement of the hands, feet, and facial features.
- Actinic keratosis
- A rough, sun-damaged skin patch that can sometimes develop into squamous cell skin cancer.
- Active immunity
- Protection generated by the body's own immune response to an antigen.
- Acupuncture
- A procedure involving insertion of thin needles at selected body sites, sometimes used for symptom management.
- Acute
- Describes a condition that begins suddenly or lasts a relatively short time; it does not necessarily mean severe.
- Acute kidney injury
- A sudden decline in kidney function that can cause waste and fluid to build up in the body.
- Acute pancreatitis
- Sudden inflammation of the pancreas that often causes severe upper abdominal pain and can require hospital care.
- Addison disease
- A condition in which the adrenal glands produce too little cortisol and often too little aldosterone.
- Adenomyosis
- A condition in which tissue similar to the uterine lining grows within the muscular wall of the uterus.
- Adenovirus infection
- An infection caused by adenoviruses that may affect the airways, eyes, or digestive system.
- Adjuvant therapy
- Treatment given after the main treatment to reduce the chance that a disease, often cancer, will return.
- Adrenal gland
- A small gland above each kidney that makes hormones including cortisol and adrenaline.
- Ageusia
- Complete loss of the sense of taste, which may occur with nerve damage, infection, or other causes.
- Agitation
- A state of increased restlessness or distress that may occur with physical or mental health conditions.
- Akathisia
- An uncomfortable sense of inner restlessness, often causing a person to feel compelled to move.
- Albumin blood test
- A laboratory measurement of albumin, a major blood protein made by the liver.
- Alkaline phosphatase test
- A blood test measuring an enzyme associated with the liver, bile ducts, and bone.
- Allergen
- A substance, such as pollen or a food protein, that can trigger an allergic reaction in a susceptible person.
- Allergy
- An immune-system reaction to a substance that is usually harmless to most people.
- Allodynia
- Pain caused by something that does not usually hurt, such as a light touch on the skin.
- Allogeneic transplant
- A transplant of cells or tissues from a genetically different person of the same species.
- Alopecia areata
- An autoimmune condition that causes patchy hair loss, sometimes affecting the scalp, eyebrows, or other body hair.
- ALT blood test
- A blood test measuring alanine aminotransferase, an enzyme that may rise when liver cells are injured.
- Alveoli
- Tiny air sacs in the lungs where oxygen enters blood and carbon dioxide leaves it.
- Alzheimer disease
- A progressive brain disorder that commonly affects memory, thinking, and the ability to carry out everyday tasks.
- Ambulatory care
- Medical services provided without admitting the patient for an overnight hospital stay.
- Amenorrhea
- The absence of menstrual periods, which may occur for normal reasons or because of a medical condition.
- Amino acid
- A building block of proteins that the body uses to make tissues, enzymes, and other important molecules.
- Amniotic fluid
- The liquid surrounding a developing fetus during pregnancy that helps cushion and protect it.
- Amylase test
- A blood or urine test measuring an enzyme involved in digesting starch, sometimes used when evaluating pancreatic disease.
- Amyloidosis
- A group of disorders in which abnormal proteins accumulate in tissues and may interfere with organ function.
- Amyotrophic lateral sclerosis
- A progressive disease affecting nerve cells that control voluntary muscles, causing increasing weakness.
- Anal fissure
- A small tear in the lining of the anus that can cause pain and bleeding during bowel movements.
- Anal fistula
- An abnormal tunnel between the anal canal and nearby skin, often developing after an infection.
- Anaphylaxis
- A severe and potentially life-threatening allergic reaction that can affect breathing and circulation.
- Anasarca
- Severe, widespread swelling caused by fluid accumulating throughout the body's tissues.
- Anemia
- A condition in which the blood has too little hemoglobin or too few healthy red blood cells to carry oxygen effectively.
- Aneurysm
- A weakened area of a blood vessel wall that bulges outward and may sometimes rupture.
- Angina
- Chest discomfort caused by insufficient oxygen-rich blood reaching the heart muscle, often during exertion.
- Angiography
- Imaging of blood vessels using contrast material or specialized scanning techniques.
- Angioplasty
- A procedure that widens a narrowed blood vessel, often using an inflatable balloon.
- Anisocoria
- A difference in pupil size between the two eyes, which may be normal or signal a medical problem.
- Ankle-brachial index
- A comparison of blood pressure at the ankle and arm used to screen for reduced blood flow to the legs.
- Ankylosing spondylitis
- An inflammatory arthritis that mainly affects the spine and may cause long-term back pain and stiffness.
- Anorexia nervosa
- An eating disorder involving restricted food intake, intense fear of weight gain, and distorted body image.
- Anosmia
- Loss of the sense of smell, which may happen after infections, injury, or other conditions.
- Antacid
- A medicine that neutralizes stomach acid and can provide short-term relief from heartburn.
- Antibiotic
- A medicine used to treat certain bacterial infections; antibiotics do not treat viral infections.
- Antibody
- A protein made by the immune system that recognizes a specific target, such as part of a germ.
- Anticholinergic
- A medicine that blocks the effects of acetylcholine at certain receptors and can affect secretions, bladder, and gut activity.
- Anticoagulant
- A medicine that lowers the likelihood of blood clot formation or growth.
- Anticoagulation
- Treatment that reduces the blood's ability to form clots, often used to prevent stroke or venous thrombosis.
- Anticonvulsant
- A medicine used to prevent or reduce certain types of seizures, also used for some other conditions.
- Antidepressant
- A medicine used to treat depression and sometimes anxiety or other conditions by affecting brain signaling.
- Antiemetic
- A medicine used to prevent or relieve nausea and vomiting.
- Antifungal
- A medicine used to treat infections caused by fungi, such as yeasts or molds.
- Antigen
- A substance recognized by the immune system that may trigger or bind an immune response.
- Antihistamine
- A medicine that blocks certain effects of histamine, often used to manage allergy symptoms.
- Antihypertensive
- A medicine used to lower high blood pressure through one of several mechanisms.
- Antimicrobial resistance
- The ability of microorganisms to survive medicines that would ordinarily kill or inhibit them.
- Antinuclear antibody test
- A blood test that detects certain antibodies that may occur in autoimmune diseases.
- Antioxidant
- A substance that can help limit damage caused by certain reactive molecules called free radicals.
- Antiplatelet drug
- A medicine that makes platelets less likely to stick together and form blood clots.
- Antipsychotic
- A medicine used for psychosis and some other mental health conditions by changing brain neurotransmitter activity.
- Antipyretic
- A medicine that lowers fever, such as acetaminophen or ibuprofen.
- Antiseptic
- A substance applied to skin or living tissue to reduce microorganisms.
- Antispasmodic
- A medicine used to reduce certain muscle spasms, sometimes including those in the digestive tract.
- Antiviral
- A medicine that interferes with the replication or activity of particular viruses.
- Anuria
- Production of very little or essentially no urine, sometimes indicating a serious urinary or kidney problem.
- Aorta
- The largest artery in the body, carrying oxygen-rich blood from the heart to the circulation.
- Aortic dissection
- A serious tear in the inner layer of the aorta that allows blood to separate layers of its wall.
- Aortic regurgitation
- Leakage of blood backward through the aortic valve when it does not close completely.
- Aortic stenosis
- Narrowing of the heart's aortic valve, which makes it harder for blood to leave the heart.
- Aortic valve
- The heart valve controlling blood flow from the left ventricle into the aorta.
- Apgar score
- A quick assessment of a newborn's condition shortly after birth using breathing, heart rate, muscle tone, reflexes, and color.
- Aphasia
- A language disorder caused by brain injury that can affect speaking, understanding, reading, or writing.
- Apnea
- A temporary pause in breathing that may occur during sleep or other circumstances.
- Apoptosis
- An orderly process of programmed cell death that helps remove unneeded or damaged cells.
- Appendicitis
- Inflammation of the appendix that often causes abdominal pain and may require urgent surgery.
- Appendix
- A narrow pouch connected to the beginning of the large intestine in the lower right abdomen.
- Apraxia
- Difficulty performing learned purposeful movements despite having the necessary basic strength and understanding.
- ARB
- An angiotensin receptor blocker, a medicine that lowers blood pressure by limiting angiotensin II effects.
- Aromatase inhibitor
- A medicine that reduces estrogen production, often used in certain hormone-sensitive breast cancers.
- Arrhythmia
- A heart rhythm that is faster, slower, or more irregular than normal.
- Arterial blood gas
- A blood test measuring oxygen, carbon dioxide, and acidity to evaluate breathing and metabolic balance.
- Artery
- A blood vessel that carries blood away from the heart, usually under relatively high pressure.
- Arthritis
- Inflammation or disease affecting one or more joints, often causing pain, swelling, or stiffness.
- Arthrocentesis
- A procedure that uses a needle to withdraw fluid from a joint for testing or symptom relief.
- Arthroscopy
- A minimally invasive procedure using a camera inserted into a joint to examine or treat problems.
- Ascites
- An abnormal buildup of fluid inside the abdominal cavity, often associated with liver disease.
- Aspiration
- In medicine, either drawing fluid through a needle or accidentally inhaling material into the airways.
- AST blood test
- A blood test measuring aspartate aminotransferase, an enzyme found in liver and other tissues.
- Asthma
- A long-term condition in which the airways become inflamed and narrowed, causing episodes of wheezing, cough, or breathlessness.
- Ataxia
- Loss of coordinated movement that may affect walking, balance, speaking, or hand movements.
- Atherosclerosis
- A condition in which fatty plaques accumulate in artery walls and may restrict blood flow.
- Atherosclerotic plaque
- A buildup of fats, inflammatory cells, and fibrous material in the wall of an artery.
- Atopic dermatitis
- A chronic, itchy inflammatory skin condition that often begins in childhood.
- Atrial fibrillation
- A common irregular heart rhythm that increases the risk of blood clots and stroke.
- Atrial flutter
- A fast, organized abnormal rhythm arising from electrical circuits in the upper chambers of the heart.
- Atrioventricular block
- A delay or interruption of electrical signals traveling from the atria to the ventricles.
- Atrium
- One of the two upper chambers of the heart that receives blood returning to the heart.
- Audiometry
- Testing used to measure hearing sensitivity across different sound frequencies.
- Autism spectrum disorder
- A neurodevelopmental condition involving differences in social communication, behavior, and sensory processing.
- Autoimmune disease
- A condition in which the immune system mistakenly attacks the body's own tissues.
- Autologous transplant
- Transplantation of a person's own cells or tissues back into that same person.
- Autonomic nervous system
- The part of the nervous system regulating automatic functions such as heart rate, digestion, and sweating.
- Axillary lymph nodes
- Lymph nodes in the armpit that help filter lymph from the arm, chest, and breast.
B
- B cell
- A type of lymphocyte that can develop into antibody-producing plasma cells.
- Bacteremia
- The presence of bacteria in the bloodstream, which may be temporary or associated with serious infection.
- Bacterial vaginosis
- An imbalance of the bacteria normally present in the vagina, sometimes causing discharge or odor.
- Bacterium
- A single-celled microorganism; some bacteria are helpful while others can cause disease.
- Bariatric surgery
- A group of operations that alter the digestive tract to treat obesity and improve related health conditions.
- Barrett esophagus
- A change in cells lining the lower esophagus, often associated with long-standing acid reflux.
- Basal ganglia
- Groups of brain structures involved in movement, learning, and certain behaviors.
- Basal insulin
- Insulin that provides background coverage between meals and overnight.
- Basal metabolic rate
- An estimate of the energy the body uses at rest to maintain basic functions.
- Bell palsy
- A sudden weakness or paralysis of muscles on one side of the face caused by facial nerve dysfunction.
- Benign
- Not cancerous; a benign growth does not invade nearby tissues or spread to distant parts of the body.
- Benzodiazepine
- A medicine that enhances the effect of GABA in the brain and may be used for anxiety, seizures, or sedation.
- Beta blocker
- A medicine that reduces the effects of adrenaline-like signals on the heart and other tissues.
- Beta-2 agonist
- A medicine that stimulates beta-2 receptors and relaxes smooth muscle in the airways.
- Bilateral
- A medical description meaning that both sides of the body or both members of a paired structure are affected.
- Bile
- A digestive fluid made by the liver that helps break down and absorb dietary fats.
- Bile acid
- A substance produced from cholesterol by the liver that helps the intestine absorb fats.
- Bile acid sequestrant
- A medicine that binds bile acids in the intestine and can lower LDL cholesterol or treat certain bile-acid-related diarrhea.
- Bile duct
- A tube that carries bile from the liver or gallbladder toward the small intestine.
- Bilirubin test
- A blood test measuring bilirubin, a pigment produced when red blood cells break down.
- Biofilm
- A community of microorganisms attached to a surface and surrounded by a protective matrix.
- Biologic medicine
- A treatment derived from living systems or made using biotechnology, often targeting a specific biological process.
- Biomarker
- A measurable biological characteristic that can indicate a normal process, disease, or response to treatment.
- Biopsy
- A procedure in which a small sample of tissue or cells is collected and examined to help diagnose a condition.
- Bipolar disorder
- A mood disorder involving episodes of depression and episodes of mania or hypomania.
- Birth defect
- A structural or functional difference present at birth that may affect health or development.
- Bisphosphonate
- A medicine that slows bone breakdown and is often used to treat osteoporosis.
- Bladder
- A hollow muscular organ that stores urine before it leaves the body.
- Bladder cancer
- Cancer that begins in the tissues lining or forming the urinary bladder.
- Bleeding gums
- Bleeding from gum tissue that may result from gingivitis, injury, or other medical conditions.
- Blepharitis
- Inflammation along the eyelid edges that can cause redness, irritation, and crusting.
- Blood culture
- A laboratory test that checks a blood sample for bacteria or fungi that may cause infection.
- Blood glucose
- The amount of sugar called glucose circulating in the blood.
- Blood oxygen saturation
- An estimate of the percentage of hemoglobin carrying oxygen, often measured by pulse oximetry.
- Blood pressure
- The force of circulating blood pushing against artery walls, usually reported as systolic over diastolic pressure.
- Blood transfusion
- Administration of donated blood or blood components into a person's circulation.
- Blood-brain barrier
- A protective system of cells that controls the movement of many substances from the blood into the brain.
- Body composition
- The relative amounts of fat, muscle, bone, water, and other components that make up the body.
- Body mass index
- A screening measure calculated from height and weight; it does not directly measure body fat or overall health.
- Bone density scan
- An imaging test, commonly DXA, that estimates bone mineral density and helps assess fracture risk.
- Bone marrow
- Soft tissue inside many bones where blood cells are produced.
- Bone marrow transplant
- A treatment that replaces or restores blood-forming stem cells after intensive therapy or in certain diseases.
- Botulism
- A rare but serious illness caused by botulinum toxin that can lead to muscle weakness and paralysis.
- Bradycardia
- A heart rate that is slower than expected for the person's age and circumstances.
- Bradykinesia
- Unusually slow voluntary movement, commonly seen in Parkinson disease and some other neurological disorders.
- Brainstem
- The lower part of the brain that connects to the spinal cord and helps control breathing and other essential functions.
- Braxton Hicks contractions
- Intermittent uterine tightening during pregnancy that does not necessarily indicate active labor.
- Breast ultrasound
- An imaging examination using sound waves to assess tissue within the breast.
- Breathlessness
- A feeling of difficult or uncomfortable breathing, also known as shortness of breath or dyspnea.
- Breech presentation
- A fetal position in which the buttocks or feet are closest to the birth canal rather than the head.
- Bronchi
- The larger air passages that branch from the windpipe into the lungs.
- Bronchiectasis
- Permanent widening and damage of airways that can lead to ongoing cough and repeated lung infections.
- Bronchioles
- Small branching airways inside the lungs that lead toward the air sacs.
- Bronchitis
- Inflammation of the bronchial tubes, often causing a cough and sometimes mucus production.
- Bronchodilator
- A medicine that relaxes airway muscles to help open narrowed breathing passages.
- Bronchoscopy
- A procedure using a thin camera to examine the airways within the lungs.
- Bruising
- Discoloration from blood leaking under the skin after injury or because of certain bleeding conditions.
- Bulimia nervosa
- An eating disorder involving repeated binge eating followed by attempts to compensate, such as vomiting or misuse of laxatives.
- BUN test
- A blood test measuring urea nitrogen, a waste product affected by kidney function and other factors.
- Bundle branch block
- A delay in electrical conduction through one of the pathways activating the heart's ventricles.
- Bunion
- A bony prominence at the base of the big toe, often associated with the toe angling toward the others.
- Bursitis
- Inflammation of a small fluid-filled sac that cushions tendons and joints.
C
- C-peptide test
- A blood test measuring a substance released with insulin, which can help assess the body's insulin production.
- C-reactive protein test
- A blood test measuring a protein that rises with inflammation, infection, or tissue injury.
- Cachexia
- A complex syndrome involving unintended weight loss and muscle wasting, often associated with serious chronic illness.
- Calcium blood test
- A laboratory measurement of calcium in blood, used to evaluate bone, kidney, and hormone-related conditions.
- Calcium channel blocker
- A medicine that relaxes blood vessels or affects heart activity by limiting calcium movement into cells.
- Calorie
- A unit of energy used to describe the energy supplied by food and used by the body.
- Capillary
- A tiny blood vessel where oxygen, nutrients, and wastes are exchanged with tissues.
- Carbohydrate
- A nutrient group that includes sugars, starches, and fiber, supplying energy and other functions.
- Cardiac arrest
- A sudden loss of effective heart pumping, causing collapse and requiring immediate emergency treatment.
- Cardiac catheterization
- A procedure using a thin tube inside blood vessels to examine or treat the heart and its circulation.
- Cardiac output
- The volume of blood pumped by the heart each minute, determined by heart rate and stroke volume.
- Cardiac rehabilitation
- A supervised program of exercise, education, and support after certain heart conditions or procedures.
- Cardiogenic shock
- A life-threatening state in which severe heart dysfunction prevents adequate blood flow to organs.
- Cardiomyopathy
- A disease of the heart muscle that can affect its size, structure, or pumping function.
- Cardiovascular disease
- A broad term for conditions affecting the heart or blood vessels, including coronary artery disease and stroke.
- Cardioversion
- A treatment that restores a more normal heart rhythm using electricity or specific medications.
- Carotid artery
- One of the major arteries in the neck supplying blood to the brain and head.
- Carotid stenosis
- Narrowing of a carotid artery, often from plaque, that can increase stroke risk.
- Carotid ultrasound
- A sound-wave examination that evaluates blood flow and plaque in the carotid arteries.
- Carpal tunnel syndrome
- Compression of the median nerve at the wrist, often causing tingling or numbness in the hand.
- Carrier
- A person who harbors an infectious organism or genetic variant, sometimes without showing symptoms.
- Case fatality ratio
- The proportion of identified cases of a particular disease that result in death during a specified period.
- Cataract
- Clouding of the eye's natural lens that can cause blurry vision and glare.
- Cataract surgery
- An operation to replace a cloudy natural eye lens with an artificial lens.
- Cecum
- The pouch-like first part of the large intestine that receives material from the small intestine.
- Celiac disease
- An autoimmune disorder in which gluten triggers injury to the lining of the small intestine.
- Cell membrane
- The thin boundary surrounding a cell that controls movement of substances in and out.
- Cellulase
- An enzyme that breaks down cellulose, a major component of plant cell walls.
- Cellulitis
- A bacterial infection of the deeper skin layers that usually causes spreading redness, warmth, and tenderness.
- Central nervous system
- The brain and spinal cord, which process and coordinate information throughout the body.
- Cerebellum
- The part of the brain that helps coordinate movement, posture, and balance.
- Cerebral cortex
- The outer layer of the cerebrum involved in perception, movement, language, and thinking.
- Cerebral edema
- Swelling of brain tissue from excess fluid that can increase pressure inside the skull.
- Cerebral palsy
- A group of movement and posture disorders caused by injury or differences in the developing brain.
- Cerebrum
- The largest part of the brain, responsible for many functions including movement, sensation, memory, and language.
- Cervical cancer
- Cancer that begins in the cervix, frequently linked to persistent infection with high-risk human papillomavirus types.
- Cervical dilation
- Opening of the cervix during labor, measured in centimeters.
- Cervical radiculopathy
- Pain, tingling, numbness, or weakness caused by irritation of a nerve root in the neck.
- Cervical screening
- Testing intended to identify HPV infection or abnormal cervical changes before cancer develops.
- Cervix
- The lower, narrow portion of the uterus that opens into the vagina.
- Cesarean delivery
- Surgical childbirth through incisions in the abdomen and uterus.
- Chemotherapy
- Treatment with drugs that kill or slow rapidly dividing cells, commonly used against cancer.
- Chest CT scan
- A series of computer-processed X-ray images showing detailed structures within the chest.
- Chest X-ray
- An imaging test using a small dose of radiation to examine the lungs, heart, and chest bones.
- Chloride blood test
- A test measuring chloride, an electrolyte involved in fluid and acid-base balance.
- Cholecystectomy
- Surgical removal of the gallbladder, often performed for symptomatic gallstones or gallbladder inflammation.
- Cholecystitis
- Inflammation of the gallbladder, often caused by a gallstone blocking its outlet.
- Cholelithiasis
- The medical term for gallstones, which are hardened deposits that form inside the gallbladder.
- Cholesterol
- A waxy substance used to build cells and hormones; high levels of certain blood lipoproteins can raise cardiovascular risk.
- Cholesterol absorption
- The process by which cholesterol from food and bile enters intestinal cells and the circulation.
- Cholinesterase inhibitor
- A medicine that slows the breakdown of acetylcholine and is used for certain neurological conditions.
- Chromosome
- A structure made of DNA and proteins that carries many genes within a cell.
- Chronic
- Describes a condition that persists or recurs over a long period, often months or years.
- Chronic fatigue syndrome
- Also called ME/CFS, a long-term illness involving substantial fatigue and worsening symptoms after activity.
- Chronic kidney disease
- Kidney damage or reduced kidney function lasting at least three months, sometimes progressing over time.
- Chronic lymphocytic leukemia
- A usually slow-growing blood cancer involving abnormal mature-looking lymphocytes.
- Chronic myeloid leukemia
- A blood cancer in which the bone marrow produces too many myeloid white blood cells.
- Chylomicron
- A lipoprotein particle that transports absorbed dietary fats from the intestine through the body.
- Cirrhosis
- Advanced liver scarring that disrupts the liver's normal structure and function.
- Clavicle
- The collarbone, connecting the breastbone to the shoulder region.
- Clinical remission
- A period when signs and symptoms of a disease have substantially decreased or disappeared.
- Clinical trial
- A research study involving people to evaluate medical interventions, tests, or care approaches.
- Clostridioides difficile infection
- A bacterial intestinal infection that can cause diarrhea and inflammation of the colon, often after antibiotic exposure.
- Clotting factor
- A protein involved in the chain of reactions that helps blood form a stable clot.
- Clubbing
- Enlargement and rounding of the fingertips or toes, sometimes associated with lung or heart disease.
- Coagulation panel
- A group of tests assessing how blood clots, often including PT and aPTT.
- Coarctation of the aorta
- A congenital narrowing of part of the aorta that can increase blood pressure and strain the heart.
- Cochlea
- The spiral-shaped part of the inner ear that converts sound vibrations into nerve signals.
- Cognitive behavioral therapy
- A structured psychotherapy that helps people change unhelpful thinking and behavior patterns.
- Colitis
- Inflammation of the colon that can occur with infection, inflammatory bowel disease, or reduced blood flow.
- Colon
- The main portion of the large intestine, which absorbs water and helps form stool.
- Colon cancer
- Cancer that develops in the large intestine, often from abnormal growths called polyps.
- Colonoscopy
- A procedure that uses a flexible camera to examine the lining of the colon and rectum.
- Colostomy
- A surgically created opening bringing part of the colon to the surface of the abdomen for stool to leave the body.
- Colostrum
- The thick early breast milk produced around childbirth that contains nutrients and immune components.
- Comorbidity
- An additional disease or condition present in a person who has another main condition.
- Complete blood count
- A blood test measuring red cells, white cells, platelets, and related blood cell indices.
- Complex carbohydrate
- A carbohydrate made from chains of sugar units, such as starch; its health effects depend on food source and processing.
- Concussion
- A traumatic brain injury that temporarily affects brain function, often after a blow or jolt to the head.
- Confusion
- Difficulty thinking clearly or understanding one's surroundings that can have many causes.
- Congenital
- Present at birth, whether caused by genetics, environmental exposures, or developmental factors.
- Congenital heart disease
- A structural problem with the heart or major blood vessels that is present from birth.
- Congenital hypothyroidism
- Low thyroid hormone levels present at birth that can affect growth and development if untreated.
- Conjunctivitis
- Inflammation of the conjunctiva, the thin tissue covering the white of the eye and lining the eyelids.
- Conservative treatment
- A care approach that begins with nonsurgical or less invasive methods when appropriate.
- Constipation
- Having bowel movements that are difficult to pass, infrequent, or associated with hard stools.
- Contagious
- Able to spread from one person to another through direct or indirect transmission.
- Contraception
- Methods used to reduce the chance of pregnancy, including barrier, hormonal, and long-acting options.
- COPD
- Chronic obstructive pulmonary disease: a long-term lung condition that limits airflow, commonly including emphysema or chronic bronchitis.
- Cornea
- The clear front surface of the eye that helps focus light onto the retina.
- Coronary artery
- An artery supplying blood and oxygen to the heart muscle.
- Coronary artery disease
- Narrowing or blockage of the arteries supplying the heart muscle, usually due to plaque buildup.
- Coronary bypass surgery
- An operation that creates new routes for blood to flow around blocked coronary arteries.
- Corticosteroid
- A medicine related to cortisol that reduces inflammation or replaces hormones the body cannot produce.
- Cortisol
- A hormone produced by the adrenal glands that helps regulate stress responses, metabolism, and inflammation.
- Cough suppressant
- A medicine intended to reduce the urge to cough, with usefulness depending on the cause of cough.
- Cranial nerve
- One of twelve pairs of nerves arising from the brain or brainstem that control functions of the head and other areas.
- Craniotomy
- An operation in which a surgeon temporarily removes part of the skull to reach the brain.
- Creatine kinase test
- A blood test measuring an enzyme that may increase after muscle injury or inflammation.
- Creatinine blood test
- A laboratory measurement of creatinine, often used to help estimate kidney filtration function.
- Crohn disease
- A form of inflammatory bowel disease that can affect any part of the digestive tract.
- Cryotherapy
- Treatment using very cold temperatures to freeze tissue or reduce certain symptoms.
- CT angiography
- A CT scan performed with contrast dye to show blood vessels and evaluate narrowing or other abnormalities.
- Cushing syndrome
- A condition caused by prolonged exposure to excessive cortisol, whether produced by the body or taken as medication.
- Cyanosis
- A bluish or grayish discoloration of skin or mucous membranes associated with low oxygen or circulation changes.
- Cyst
- A closed sac in tissue that may contain fluid, air, or other material.
- Cystic fibrosis
- An inherited disorder affecting the movement of salt and water across cells, causing thick secretions in organs including the lungs.
- Cytokine
- A signaling protein released by cells that helps coordinate immune responses and other biological activities.
- Cytology
- The study or examination of individual cells, often to identify abnormal or cancerous changes.
D
- D-dimer test
- A blood test measuring fragments from clot breakdown that can help assess suspected blood clots in appropriate settings.
- Debridement
- Removal of dead, infected, or damaged tissue to help a wound heal.
- Decongestant
- A medicine that temporarily reduces swelling in the nasal passages to relieve stuffiness.
- Decreased appetite
- A reduced desire to eat that may occur with illness, medicines, mood changes, or other conditions.
- Deep vein thrombosis
- A blood clot that forms in a deep vein, usually in the leg, and may travel to the lungs.
- Dehydration
- A state in which the body has lost more fluid than it takes in, potentially affecting normal functions.
- Delayed puberty
- Pubertal development that begins later than expected for age, sometimes requiring medical assessment.
- Delirium
- A sudden change in attention and awareness, often caused by illness, medications, or other medical problems.
- Dementia
- A syndrome involving decline in memory or other thinking abilities severe enough to interfere with daily life.
- Dental abscess
- A collection of pus caused by infection in or around a tooth or its supporting tissues.
- Dermatitis
- Inflammation of the skin that can cause redness, itching, scaling, or irritation.
- Dermatomyositis
- An inflammatory disease that can cause muscle weakness and a characteristic skin rash.
- DEXA scan
- A low-dose X-ray technique used to measure bone density and sometimes body composition.
- Diabetes mellitus
- A group of conditions characterized by persistently high blood glucose due to problems with insulin production or action.
- Diabetic ketoacidosis
- A medical emergency in which insulin deficiency causes high levels of ketones and acid to build up in the blood.
- Diabetic neuropathy
- Nerve damage associated with diabetes that may cause tingling, pain, numbness, or weakness.
- Diabetic retinopathy
- Damage to retinal blood vessels caused by diabetes that can threaten vision.
- Dialysis
- Treatment that removes waste products and excess fluid from blood when the kidneys cannot do so adequately.
- Diaphragm
- The dome-shaped muscle below the lungs that plays a central role in breathing.
- Diarrhea
- Passing loose or watery stools more frequently than normal.
- Diastolic dysfunction
- Impaired relaxation or filling of a heart ventricle, sometimes contributing to heart failure symptoms.
- Diastolic pressure
- The lower blood pressure number, representing pressure in the arteries while the heart relaxes between beats.
- Dietary counseling
- Professional guidance to help a person adjust eating patterns for health, nutrition, or medical treatment.
- Dietary fiber
- Plant carbohydrates that resist digestion in the small intestine and can support bowel and metabolic health.
- Dilation and curettage
- A procedure involving opening the cervix and removing tissue from inside the uterus.
- Diplopia
- Seeing two images of a single object, commonly called double vision.
- Disorientation
- Difficulty recognizing the time, location, situation, or people around oneself.
- Diuretic
- A medicine that increases urine production and helps the body remove excess salt or water.
- Diverticulitis
- Inflammation of small pouches in the colon wall that may cause abdominal pain and fever.
- Diverticulosis
- The presence of small pouches in the colon wall, which often cause no symptoms.
- Dizziness
- A general term for feeling lightheaded, unsteady, or as though the surroundings are moving.
- DNA
- Deoxyribonucleic acid, the molecule carrying genetic instructions in most cells and many organisms.
- Dominant inheritance
- A pattern in which one disease-associated copy of a gene can be sufficient to cause a trait or disorder.
- Dosage form
- The physical form of a medicine, such as a tablet, capsule, cream, or injection.
- Dose
- The amount of medicine administered at one time or according to a specified schedule.
- Down syndrome
- A genetic condition usually caused by an extra copy of chromosome 21 and associated with characteristic developmental and health differences.
- Drainage
- A procedure that removes accumulated fluid, blood, or pus from a body space or tissue.
- Drug allergy
- An immune-mediated reaction to a medication, ranging from a rash to a potentially severe reaction.
- Drug interaction
- A change in the effect of a medicine caused by another drug, food, supplement, or substance.
- Drug tolerance
- Reduced response to a medicine after repeated exposure, sometimes requiring reassessment of treatment.
- Duodenum
- The first segment of the small intestine immediately after the stomach.
- Dysarthria
- Slurred or poorly articulated speech caused by difficulty controlling the muscles used for speaking.
- Dysgeusia
- An altered sense of taste, such as a persistent metallic, bitter, or unusual taste.
- Dyslexia
- A learning disorder that primarily affects accurate or fluent word reading and spelling.
- Dysmenorrhea
- Painful menstrual cramps that occur before or during menstruation.
- Dysphagia
- Difficulty swallowing food, liquids, or saliva that may increase the risk of choking or aspiration.
- Dyspnea
- The medical term for shortness of breath or an uncomfortable awareness of breathing.
- Dysuria
- Pain or burning while urinating, often associated with urinary tract irritation or infection.
E
- Eardrum
- A thin membrane that vibrates in response to sound and separates the outer ear from the middle ear.
- Ecchymosis
- A flat area of skin discoloration caused by blood leaking from vessels into surrounding tissue.
- Echocardiogram
- An ultrasound examination that shows the heart's chambers, valves, and pumping function.
- Eclampsia
- Seizures related to preeclampsia during pregnancy or after delivery that are not better explained by another cause.
- Ectopic pregnancy
- A pregnancy that implants outside the uterine cavity, most commonly in a fallopian tube, and can be life-threatening.
- Eczema
- A group of inflammatory skin conditions that cause itchy, dry, or irritated skin; atopic dermatitis is a common type.
- Edema
- Swelling caused by an abnormal buildup of fluid in body tissues.
- Ejection fraction
- The percentage of blood in a heart ventricle pumped out during each contraction.
- Elective surgery
- An operation scheduled in advance rather than performed immediately as an emergency.
- Electrocardiogram
- A test, also called an ECG or EKG, that records the heart's electrical activity.
- Electroencephalogram
- A test that records electrical activity in the brain using electrodes placed on the scalp.
- Electrolyte
- A mineral that carries an electrical charge in body fluids, such as sodium, potassium, or chloride.
- Electrolyte imbalance
- An abnormal level of one or more charged minerals in body fluids that can affect nerves, muscles, or organs.
- Electromyography
- A test recording electrical activity in muscles to help investigate nerve or muscle disorders.
- Embolism
- Blockage of a blood vessel by material, such as a blood clot, that has traveled through the bloodstream.
- Embryo
- The developing human organism during the early weeks after fertilization, before the fetal stage.
- Encephalitis
- Inflammation of the brain that can result from infection or an immune reaction.
- Encephalopathy
- A broad term for altered brain function due to illness, injury, toxins, or metabolic disturbances.
- End-diastolic volume
- The volume of blood inside a ventricle just before it contracts.
- Endemic
- Consistently present at an expected level within a particular geographic area or population.
- Endocarditis
- Inflammation or infection of the inner lining of the heart, commonly involving heart valves.
- Endometrial biopsy
- A procedure that collects a small sample of uterine lining for laboratory examination.
- Endometrial cancer
- Cancer arising from the lining of the uterus, often presenting with abnormal vaginal bleeding.
- Endometriosis
- A condition in which tissue similar to the uterine lining grows outside the uterus, often causing pelvic pain.
- Endometrium
- The inner lining of the uterus that changes during the menstrual cycle and is shed during menstruation.
- Endoscopy
- A procedure using a thin viewing instrument to examine the inside of an organ or body cavity.
- Endotracheal intubation
- Placement of a tube through the mouth or nose into the windpipe to maintain an airway.
- Energy expenditure
- The amount of energy the body uses for basic functions, digestion, and physical activity.
- Enteral nutrition
- Delivery of nutrients through the digestive tract, by mouth or through a feeding tube.
- Enzyme
- A protein or other molecule that speeds a chemical reaction without being used up in the process.
- Epidemic
- An increase in disease cases above the level normally expected in a population or area.
- Epidemiology
- The study of how health events are distributed in populations and what factors influence them.
- Epidermis
- The outermost layer of skin that helps protect the body from the environment.
- Epididymis
- A coiled tube behind each testicle where sperm mature and are stored.
- Epidural anesthesia
- Administration of anesthetic medicines near spinal nerves to reduce sensation in part of the body.
- Epilepsy
- A neurological disorder characterized by an ongoing tendency to have unprovoked seizures.
- Erectile dysfunction
- Persistent difficulty getting or maintaining an erection firm enough for sexual activity.
- Erythema
- Redness of the skin caused by increased blood flow in superficial blood vessels.
- Erythrocyte sedimentation rate
- A blood test measuring how quickly red blood cells settle, sometimes used as a nonspecific inflammation marker.
- Esophageal cancer
- Cancer that begins in the esophagus, the tube carrying food from the mouth to the stomach.
- Esophagus
- The muscular tube that carries swallowed food and liquids from the throat to the stomach.
- Essential fatty acid
- A fat the body cannot make in sufficient amounts and therefore must obtain from food.
- Essential tremor
- A common movement disorder that causes rhythmic shaking, often of the hands during activity.
- Estimated glomerular filtration rate
- An estimate of kidney filtering capacity calculated from blood creatinine or other markers and personal factors.
- Estrogen
- A group of hormones involved in reproductive function, bone health, and other body processes.
- Etiology
- The underlying cause or origin of a disease or medical condition.
- Exacerbation
- A temporary worsening of a long-term illness or its symptoms.
- Excessive thirst
- An unusually strong desire to drink fluids, sometimes called polydipsia.
- Excision
- Surgical removal of a lesion, tissue, or other structure.
- Exercise intolerance
- Difficulty performing physical activity at a level previously tolerated, potentially due to heart, lung, muscle, or other problems.
- Expectorant
- A medicine intended to help loosen or clear mucus from the airways.
- Extracorporeal shock wave lithotripsy
- A treatment using shock waves from outside the body to break certain kidney stones into smaller pieces.
F
- Facial droop
- Uneven movement or sagging on one side of the face that can be a sign of stroke or facial nerve dysfunction.
- Fainting
- A brief loss of consciousness from reduced blood flow to the brain, also called syncope.
- Fallopian tube
- A tube connecting the region of each ovary to the uterus, where fertilization usually occurs.
- Fasting blood glucose
- The concentration of glucose in the blood measured after a period without calories.
- Fat-soluble vitamin
- A vitamin absorbed with dietary fat, including vitamins A, D, E, and K.
- Fatigue
- A persistent feeling of tiredness or lack of energy that may not improve fully with rest.
- Fatty acid
- A molecule that forms part of many fats and serves as an energy source or cell component.
- Fatty liver disease
- A condition involving excess fat in liver cells, which may or may not be accompanied by inflammation or scarring.
- Febrile seizure
- A seizure associated with fever, most often occurring in young children without a central nervous system infection.
- Fecal calprotectin
- A stool test measuring a protein linked to intestinal inflammation.
- Fecal occult blood test
- A stool screening test that looks for traces of blood not visible to the eye.
- Femur
- The thighbone, extending from the hip to the knee and forming the body's longest bone.
- Ferritin test
- A blood test measuring ferritin, a protein that reflects iron stores but also rises with inflammation.
- Fetal growth restriction
- A condition in which a fetus does not reach its expected growth potential, often related to placental problems.
- Fetus
- The developing offspring from the fetal stage of pregnancy until birth.
- Fever
- A body temperature above the usual range, often occurring as part of the body's response to an infection.
- Fibrinogen test
- A blood test measuring fibrinogen, a protein involved in blood clot formation.
- Fibrinolytic drug
- A medicine that breaks down fibrin in blood clots, used in selected medical emergencies.
- Fibroids
- Noncancerous growths of muscle and connective tissue in the uterus that may cause bleeding or pressure symptoms.
- Fibromyalgia
- A long-term condition involving widespread pain, often alongside fatigue, sleep difficulties, or cognitive symptoms.
- Fibula
- The thinner of the two long bones in the lower leg, located on the outer side.
- First trimester
- The earliest stage of pregnancy, generally covering the first 13 completed weeks.
- Flatulence
- The passage of gas from the intestines through the anus.
- Flushing
- Temporary warmth and redness of the skin, commonly involving the face or neck.
- Focal seizure
- A seizure that begins in one area or network on one side of the brain.
- Folate test
- A test measuring folate levels to help investigate certain types of anemia or nutritional deficiency.
- Folliculitis
- Inflammation of hair follicles, sometimes caused by infection, friction, or irritation.
- Fomite
- An object or surface that can carry infectious organisms and contribute to transmission.
- Fontanelle
- A soft gap between skull bones in an infant that gradually closes as the skull develops.
- Fracture
- A break or crack in a bone, ranging from a small stress fracture to a complete break.
- Free T4 test
- A blood test measuring unbound thyroxine, a thyroid hormone that helps regulate metabolism.
- Frequent urination
- Needing to urinate more often than usual, which can have urinary, metabolic, or other causes.
- Frontal lobe
- The front part of the brain involved in planning, decision-making, voluntary movement, and behavior.
- Fructose
- A simple sugar naturally present in fruit and honey and added to some processed foods.
G
- Gallbladder
- A small organ under the liver that stores and concentrates bile.
- Gallstone pancreatitis
- Inflammation of the pancreas caused when a gallstone blocks the flow of pancreatic or bile secretions.
- Gamma-glutamyl transferase test
- A blood test measuring GGT, an enzyme that can increase with liver or bile duct conditions.
- Gastric bypass
- A weight-loss operation that creates a small stomach pouch and reroutes part of the small intestine.
- Gastritis
- Inflammation of the stomach lining that may be caused by infection, medicines, or other factors.
- Gastroesophageal reflux disease
- GERD is a condition in which stomach contents repeatedly flow back into the esophagus and cause troublesome symptoms or complications.
- Gastroscopy
- An endoscopic examination of the esophagus, stomach, and first part of the small intestine.
- Gene
- A segment of DNA containing instructions for making a functional RNA or protein product.
- Generalized anxiety disorder
- A condition involving persistent, difficult-to-control worry about multiple areas of life.
- Generalized seizure
- A seizure that begins in networks involving both sides of the brain from the start.
- Generic medicine
- A medicine with the same active ingredient and required comparable performance as an approved brand-name reference product.
- Genetic mutation
- A change in the sequence of DNA that may be harmless, harmful, or occasionally beneficial.
- Genital herpes
- A sexually transmitted infection caused by herpes simplex virus that may cause recurrent genital sores.
- Genotype
- The genetic makeup of an organism or the particular gene variants it carries.
- Gestational age
- The length of a pregnancy, usually counted from the first day of the last menstrual period.
- Gestational diabetes
- High blood sugar first recognized during pregnancy that was not clearly present before pregnancy.
- Gingivitis
- Inflammation of the gums, often related to dental plaque, that can cause bleeding during brushing.
- Glaucoma
- A group of eye diseases that damage the optic nerve and can lead to vision loss.
- Glomerulus
- A tiny network of capillaries in the kidney that begins the process of filtering blood.
- GLP-1 receptor agonist
- A medicine that mimics glucagon-like peptide-1 and can improve glucose control and sometimes promote weight loss.
- Glucagon
- A pancreatic hormone that helps raise blood glucose, particularly during fasting.
- Glucocorticoid
- A hormone or medicine that affects metabolism and immune responses, including drugs used to treat inflammation.
- Glucose
- A simple sugar that serves as a major fuel for the body's cells.
- Glucose tolerance test
- A test that measures blood glucose after a glucose drink to assess how the body handles sugar.
- Glycated hemoglobin
- Also called HbA1c, a blood measurement reflecting average glucose exposure over roughly the previous two to three months.
- Glycemic index
- A ranking of carbohydrate-containing foods by how quickly they raise blood glucose under standardized conditions.
- Glycogen
- The stored form of glucose found mainly in the liver and muscles.
- Gout
- A type of inflammatory arthritis caused by deposits of urate crystals in or around joints.
- Gram-negative bacteria
- A broad group of bacteria with a cell envelope structure that includes an outer membrane.
- Gram-positive bacteria
- Bacteria that retain a purple stain in the Gram staining procedure because of their cell-wall structure.
- Guillain-Barré syndrome
- An acute immune-mediated nerve disorder that often causes rapidly developing weakness and reduced reflexes.
H
- H2 blocker
- A medicine that lowers stomach acid production by blocking histamine H2 receptors.
- Halitosis
- The medical term for persistent or noticeable bad breath.
- Haptoglobin test
- A blood test measuring a protein that binds released hemoglobin and may be low when red cells are destroyed.
- Hashimoto thyroiditis
- An autoimmune condition that damages the thyroid gland and frequently causes hypothyroidism.
- HDL cholesterol
- Cholesterol carried by high-density lipoproteins, which participate in cholesterol transport in the body.
- Heart attack
- Damage to heart muscle caused by a sudden reduction or blockage of blood flow through a coronary artery.
- Heart block
- A disturbance in electrical conduction through the heart that may slow or interrupt signals to the ventricles.
- Heart failure
- A condition in which the heart cannot pump or fill well enough to meet the body's needs without increased pressures.
- Heart murmur
- A sound heard during heartbeat caused by turbulent blood flow, which may be harmless or associated with disease.
- Hematemesis
- Vomiting blood, which may indicate bleeding in the upper digestive tract and requires prompt assessment.
- Hematochezia
- Passing visible red or maroon blood from the rectum, often associated with lower digestive tract bleeding.
- Hematuria
- The presence of blood in urine, which may be visible or detected only by testing.
- Heme iron
- Iron present in animal foods such as meat and fish that is generally absorbed more readily than non-heme iron.
- Hemochromatosis
- A condition in which excess iron accumulates in body tissues and may damage organs.
- Hemodialysis
- A form of dialysis that circulates blood through a machine to remove waste and extra fluid.
- Hemoglobin
- The iron-containing protein in red blood cells that carries oxygen from the lungs to body tissues.
- Hemoglobin electrophoresis
- A laboratory test used to identify different forms of hemoglobin, including those associated with inherited blood disorders.
- Hemophilia
- A group of inherited bleeding disorders caused by deficiency of certain blood-clotting proteins.
- Hemoptysis
- Coughing up blood or blood-streaked mucus from the respiratory tract.
- Hemorrhage
- Bleeding caused by blood escaping from a damaged blood vessel, either inside or outside the body.
- Hemorrhoids
- Swollen vascular cushions in or around the anus that may cause bleeding, itching, or discomfort.
- Hemostasis
- The process of stopping bleeding through vessel constriction, platelet activity, and blood clotting.
- Hepatic encephalopathy
- Changes in brain function related to severe liver dysfunction or abnormal blood flow around the liver.
- Hepatitis
- Inflammation of the liver, which may result from viruses, alcohol, medicines, or other causes.
- Hereditary
- Passed from parent to child through inherited genetic information.
- Hernia
- A condition in which tissue or an organ pushes through a weak spot in surrounding muscle or connective tissue.
- Hiatal hernia
- A condition in which part of the stomach moves upward through the opening in the diaphragm.
- Hidradenitis suppurativa
- A chronic inflammatory skin condition causing painful lumps and tunnels, commonly in skin-fold areas.
- Hippocampus
- A brain structure important for forming and organizing new memories.
- Hirsutism
- Excess growth of coarse hair in a typically male pattern in women, sometimes associated with androgen excess.
- Histology
- Microscopic examination of tissue structure, often used to help diagnose disease.
- HIV infection
- Infection with human immunodeficiency virus, which weakens the immune system if not effectively treated.
- Hoarseness
- A rough, breathy, or strained voice resulting from changes in vocal cord function.
- Hodgkin lymphoma
- A cancer of the lymphatic system characterized by particular abnormal cells, including Reed–Sternberg cells.
- Holter monitor
- A wearable device that records the heart's electrical activity continuously, often for one or two days.
- Home sleep apnea test
- A portable recording of breathing-related signals during sleep used in selected people suspected of sleep apnea.
- Homeostasis
- The body's ongoing regulation of internal conditions, such as temperature, fluid balance, and blood glucose.
- Hormone
- A chemical messenger made by cells or glands that helps regulate functions in other tissues.
- Hormone replacement therapy
- Treatment that supplies hormones when the body produces too little or to manage specific hormone-related symptoms.
- Hospice care
- Care focused on comfort and quality of life for people nearing the end of life.
- Host
- A living organism that carries another organism, such as a virus, bacterium, or parasite.
- Human papillomavirus
- A group of viruses, some of which cause genital warts and others can cause certain cancers.
- Humoral immunity
- Immune protection involving antibodies produced by B cells and plasma cells.
- Hydration
- Having enough body water to support normal functions, including circulation and temperature regulation.
- Hydrocephalus
- An abnormal buildup of cerebrospinal fluid in brain cavities that can affect brain function.
- Hyperalgesia
- An increased pain response to a stimulus that normally causes pain.
- Hypercalcemia
- An abnormally high calcium level in the blood that can affect the kidneys, heart, and nervous system.
- Hyperglycemia
- A higher-than-normal blood glucose level, commonly associated with diabetes or stress responses.
- Hyperkalemia
- An excessively high potassium level in the blood that can cause dangerous heart rhythm changes.
- Hyperlipidemia
- Higher-than-desired levels of one or more blood fats, such as cholesterol or triglycerides.
- Hyperparathyroidism
- A condition in which the parathyroid glands produce too much parathyroid hormone.
- Hyperreflexia
- Reflexes that are stronger or more brisk than expected, sometimes indicating a nervous system disorder.
- Hypersomnia
- Excessive sleepiness or unusually long sleep periods that interfere with daily functioning.
- Hypertension
- Persistently elevated blood pressure that increases the risk of heart, brain, and kidney disease.
- Hyperthyroidism
- A condition in which the thyroid gland makes more thyroid hormone than the body needs.
- Hypoglycemia
- A blood glucose level that is too low, which can cause sweating, shakiness, confusion, or fainting.
- Hypokalemia
- An abnormally low potassium level in the blood that can cause weakness and heart rhythm problems.
- Hyponatremia
- A lower-than-normal sodium concentration in the blood, sometimes causing confusion or seizures.
- Hypotension
- Blood pressure that is lower than usual, sometimes causing dizziness or fainting.
- Hypothalamus
- A brain region that helps regulate body temperature, hunger, thirst, and hormone signaling.
- Hypothermia
- A dangerous drop in core body temperature, typically below 35°C or 95°F.
- Hypothyroidism
- A condition in which the thyroid gland produces too little thyroid hormone.
- Hypoxia
- A condition in which body tissues do not receive enough oxygen for normal function.
I
- Idiopathic pulmonary fibrosis
- A long-term lung disease involving progressive scarring of lung tissue without a known cause.
- Ileum
- The final portion of the small intestine, where certain nutrients including vitamin B12 are absorbed.
- Immune system
- The body's network of cells, tissues, and organs that helps defend against infections and other threats.
- Immunodeficiency
- Reduced ability of the immune system to defend against infections or other threats.
- Immunosuppressant
- A medicine that reduces immune system activity, used for transplants or certain autoimmune conditions.
- Immunotherapy
- Treatment that uses or changes the immune system to fight a disease, including some cancers and allergies.
- Impetigo
- A contagious superficial skin infection that often causes crusted sores, especially in children.
- Incidence
- The number or rate of new cases of a disease arising in a population during a defined period.
- Increased intracranial pressure
- Pressure inside the skull that is higher than normal and may affect brain function.
- Incubation period
- The time between exposure to an infectious agent and the appearance of symptoms.
- Infection
- The invasion and multiplication of harmful microorganisms in the body, sometimes causing illness.
- Inferior vena cava
- The large vein carrying blood from the lower body toward the right side of the heart.
- Infertility
- Difficulty achieving pregnancy after an appropriate period of regular unprotected intercourse or because of a known reproductive issue.
- Inflammation
- The body's response to injury or infection, which may produce redness, heat, swelling, or pain.
- Inflammatory bowel disease
- A group of disorders, including Crohn disease and ulcerative colitis, that cause ongoing inflammation in the digestive tract.
- Influenza
- A contagious respiratory illness caused by influenza viruses that can range from mild to severe.
- Inhaled corticosteroid
- An anti-inflammatory medicine delivered into the airways, commonly used for long-term asthma management.
- Innate immunity
- The body's rapid, nonspecific defense system present before exposure to a particular infection.
- Inoculation
- Introduction of material containing microorganisms or antigens into a person, animal, or laboratory system.
- INR test
- A standardized blood clotting measurement often used to monitor warfarin treatment.
- Insomnia
- Difficulty falling asleep, staying asleep, or obtaining restorative sleep despite having the opportunity.
- Insulin
- A hormone made by the pancreas that helps glucose enter cells and regulates blood sugar levels.
- Insulin analog
- A modified form of insulin designed to have a particular onset or duration of action.
- Insulin receptor
- A cell-surface protein that binds insulin and helps trigger responses involved in glucose regulation.
- Insulin resistance
- A reduced response of body cells to insulin, often requiring the pancreas to produce more insulin.
- Intermittent claudication
- Leg discomfort or pain triggered by walking and relieved by rest, commonly caused by peripheral artery disease.
- Interstitial cystitis
- A chronic condition involving bladder-associated pain or pressure and urinary symptoms without an obvious infection.
- Interstitial lung disease
- A broad group of lung disorders involving inflammation or scarring of lung tissue.
- Intervertebral disc
- A cushioning structure between spinal vertebrae that helps absorb loads and allows movement.
- Intracerebral hemorrhage
- Bleeding directly into brain tissue, a form of hemorrhagic stroke.
- Intramuscular injection
- Administration of medicine by a needle into a muscle.
- Intrauterine device
- A small device placed in the uterus to provide long-acting contraception.
- Intravenous infusion
- Delivery of fluids or medicines directly into a vein over a period of time.
- Iodine deficiency
- Too little dietary iodine to support normal thyroid hormone production.
- Iron deficiency
- A state in which the body lacks enough iron to meet its needs, sometimes leading to anemia.
- Iron panel
- A group of laboratory measurements used to evaluate iron status, sometimes including serum iron and transferrin saturation.
- Irritable bowel syndrome
- A disorder of gut–brain interaction causing recurrent abdominal pain associated with changes in bowel habits.
- Ischemia
- Inadequate blood supply to a tissue that can reduce oxygen delivery and cause injury.
- Ischemic penumbra
- Brain tissue with reduced blood flow that is at risk of injury but may still be salvageable.
- Ischemic stroke
- Brain injury caused by an interruption of blood flow to part of the brain, usually from a clot.
J
- Jaundice
- Yellowing of the skin or whites of the eyes caused by excess bilirubin in the blood.
- Jejunum
- The middle segment of the small intestine where much nutrient absorption occurs.
- Joint effusion
- An excessive accumulation of fluid within a joint, sometimes caused by injury or inflammation.
- Joint replacement
- Surgery that replaces damaged joint surfaces with artificial components.
- Joint stiffness
- Difficulty moving a joint freely, often experienced after rest or with arthritis.
K
- Kawasaki disease
- An inflammatory illness mainly affecting young children that can damage the coronary arteries.
- Keratitis
- Inflammation of the cornea that may cause eye pain, redness, light sensitivity, or reduced vision.
- Ketogenesis
- The production of ketone bodies, mainly by the liver, when the body uses fat as an important energy source.
- Ketone test
- A blood or urine test that detects ketones, substances produced when the body uses fat for energy.
- Ketonuria
- The presence of ketones in urine, which can occur with fasting, some diets, or poorly controlled diabetes.
- Ketosis
- A metabolic state in which the body produces increased amounts of ketone bodies for fuel.
- Kidney
- An organ that filters blood, regulates fluid and electrolytes, and produces urine.
- Kidney function tests
- Blood and urine measurements used to evaluate how well the kidneys filter waste and regulate body fluids.
- Kidney stone
- A hard deposit of minerals and salts that forms in the kidney or urinary tract.
L
- Labor induction
- Medical or mechanical methods used to begin labor before it starts on its own.
- Lactase
- The digestive enzyme that breaks down milk sugar, or lactose, in the small intestine.
- Lactate test
- A blood test measuring lactate, which may rise when tissues have insufficient oxygen delivery or with other conditions.
- Lactation
- The production and release of breast milk by the mammary glands.
- Lactose intolerance
- Difficulty digesting lactose, the sugar in milk, because the intestine produces too little lactase enzyme.
- Laparoscopy
- A minimally invasive surgical technique using small abdominal incisions and a camera.
- Laparotomy
- A surgical operation involving a larger incision through the abdominal wall.
- Large intestine
- The final section of the digestive tract, including the colon and rectum, that absorbs water and stores stool.
- Laryngitis
- Inflammation of the voice box that often causes hoarseness or loss of voice.
- Larynx
- The voice box, containing vocal cords and helping protect the airway during swallowing.
- Laser therapy
- Medical treatment using focused light energy to affect specific tissues.
- LDL cholesterol
- Cholesterol carried by low-density lipoproteins, high levels of which can contribute to artery plaque buildup.
- Left ventricle
- The heart's main pumping chamber that sends oxygenated blood into the aorta.
- Left ventricular hypertrophy
- Thickening of the muscle wall of the heart's left ventricle, often related to increased workload.
- Leptin
- A hormone produced mainly by fat tissue that helps signal energy stores to the brain.
- Leukemia
- A group of cancers affecting blood-forming tissues, often involving abnormal white blood cells.
- Leukocytosis
- A higher-than-normal white blood cell count that may occur with infection, inflammation, or other causes.
- Leukopenia
- A lower-than-normal white blood cell count that can sometimes increase susceptibility to infection.
- Leukotriene receptor antagonist
- A medicine that blocks inflammatory signaling from leukotrienes, sometimes used for asthma or allergic rhinitis.
- Lichen planus
- An inflammatory condition that can affect the skin, mouth, nails, or genital tissues.
- Lipase test
- A blood test measuring an enzyme made mainly by the pancreas, often used to evaluate suspected pancreatitis.
- Lipid panel
- A blood test measuring cholesterol fractions and triglycerides to help assess cardiovascular risk.
- Liver
- A large organ that processes nutrients and medicines, makes bile, and produces important blood proteins.
- Liver failure
- Severe loss of liver function that can impair blood clotting, metabolism, and toxin clearance.
- Liver function tests
- A common name for blood tests that assess liver injury and certain aspects of liver function.
- Local anesthesia
- Temporary loss of sensation in a limited body area caused by anesthetic medicine.
- Local anesthetic
- A medicine that temporarily blocks nerve signals in a small area to prevent pain during a procedure.
- Lochia
- Vaginal discharge after childbirth containing blood, mucus, and uterine tissue.
- Long COVID
- A condition in which symptoms persist or develop after a SARS-CoV-2 infection and cannot be fully explained by another cause.
- Long-acting insulin
- Insulin formulated to provide background glucose control over an extended period.
- Loop diuretic
- A diuretic acting in the kidney's loop of Henle that can remove substantial amounts of sodium and water.
- Lumbar puncture
- A procedure that collects cerebrospinal fluid from the lower back for testing or other medical purposes.
- Lumbar radiculopathy
- Symptoms caused by irritation of a nerve root in the lower spine, sometimes producing pain or numbness down a leg.
- Lung
- An organ in the chest where oxygen moves into blood and carbon dioxide is removed.
- Lupus
- A chronic autoimmune disease that may cause inflammation in the skin, joints, kidneys, and other organs.
- Lyme disease
- An infection spread by certain ticks and caused by Borrelia bacteria, sometimes affecting skin, joints, nerves, or heart.
- Lymph node
- A small immune-system structure that filters lymph fluid and helps the body respond to infections.
- Lymphadenopathy
- Enlargement or abnormal changes in lymph nodes due to infection, inflammation, cancer, or other causes.
- Lymphatic drainage
- Movement of lymph fluid through lymph vessels and nodes back toward the bloodstream.
- Lymphatic system
- A network of vessels, nodes, and organs that returns tissue fluid to circulation and supports immune defense.
- Lymphedema
- Swelling caused by impaired drainage of lymph fluid, often affecting an arm or leg.
- Lymphocyte
- A type of white blood cell involved in immune responses, including B cells and T cells.
M
- Macrolide antibiotic
- A group of antibiotics that inhibit bacterial protein production, including azithromycin and clarithromycin.
- Macronutrient
- A nutrient needed in relatively large amounts, including carbohydrate, protein, and fat.
- Macrophage
- An immune cell that engulfs debris or microbes and helps coordinate inflammation and tissue repair.
- Macula
- The central part of the retina responsible for sharp, detailed vision.
- Macular degeneration
- Damage to the central retina that can affect detailed vision needed for reading and recognizing faces.
- Malabsorption
- Difficulty absorbing nutrients from the digestive tract, potentially causing deficiencies or weight loss.
- Malaria
- A mosquito-borne infection caused by Plasmodium parasites that may cause fever and serious complications.
- Malignant
- Cancerous; a malignant tumor can invade surrounding tissues and may spread elsewhere in the body.
- Malnutrition
- A condition caused by inadequate, excessive, or imbalanced nutrient intake or use.
- Mammogram
- An X-ray image of the breast used for screening or evaluating certain breast changes.
- Mastitis
- Inflammation of breast tissue that may be associated with breastfeeding and can sometimes involve infection.
- Mean corpuscular volume
- A complete blood count measurement of the average size of red blood cells.
- Mechanical ventilation
- Use of a machine to support or replace breathing when a person cannot breathe adequately on their own.
- Medulla oblongata
- The lower brainstem region that helps control breathing, heart rate, and other automatic functions.
- Melena
- Black, tarry stool caused by digested blood, often from bleeding in the upper digestive tract.
- Memory loss
- Difficulty recalling information that can result from aging, stress, medicines, or neurological conditions.
- Meningioma
- A tumor arising from the membranes surrounding the brain or spinal cord, often slow-growing.
- Meningitis
- Inflammation of the membranes surrounding the brain and spinal cord, sometimes caused by infection.
- Menopause
- The permanent end of menstrual periods due to loss of ovarian follicle activity, diagnosed after 12 months without periods when no other cause exists.
- Metabolic syndrome
- A cluster of risk factors, including abdominal obesity, elevated blood pressure, and abnormal blood sugar or blood fats.
- Metabolism
- The chemical processes that allow the body to convert nutrients into energy and build or maintain tissues.
- Metastasis
- Spread of cancer cells from the original tumor to another location in the body.
- Metformin
- A commonly used medicine for type 2 diabetes that mainly reduces glucose production by the liver.
- Microbiome
- The collection of microorganisms and their genetic material living in a particular environment, such as the gut.
- Micronutrient
- A vitamin or mineral the body needs in relatively small amounts for normal function.
- Microorganism
- An organism too small to be seen clearly without magnification, including bacteria and many fungi.
- Migraine
- A neurological disorder involving recurrent attacks of headache, often with nausea or sensitivity to light and sound.
- Mineralocorticoid receptor antagonist
- A medicine that blocks aldosterone effects and can help in heart failure or certain blood pressure conditions.
- Miscarriage
- Spontaneous loss of a pregnancy before the stage considered viable under local clinical definitions.
- Mitral regurgitation
- Backward leakage of blood from the left ventricle into the left atrium through the mitral valve.
- Mitral stenosis
- Narrowing of the mitral valve that restricts blood flow between the left atrium and left ventricle.
- Mitral valve
- The valve between the left atrium and left ventricle that helps prevent backward blood flow.
- Monoclonal antibody
- A laboratory-made antibody designed to bind a specific target molecule.
- Monounsaturated fat
- A type of dietary fat with one double bond in its fatty acid chain, found in foods such as olive oil.
- Morbidity
- The presence or burden of illness, injury, or disability in an individual or population.
- Mortality
- Deaths in a population, often described as a number or rate over a period of time.
- MRI
- Magnetic resonance imaging: a scan using a strong magnet and radio waves to create detailed images inside the body.
- Multiple myeloma
- A cancer of plasma cells in the bone marrow that can affect bones, kidneys, and blood cell production.
- Multiple sclerosis
- An immune-mediated disease of the central nervous system that damages myelin and can cause varied neurological symptoms.
- Muscle atrophy
- A decrease in muscle size due to reduced use, nerve problems, illness, or other causes.
- Muscle fasciculation
- A brief, involuntary twitch of a small group of muscle fibers, sometimes visible beneath the skin.
- Muscle relaxant
- A medicine used to reduce certain types of muscle spasm or spasticity.
- Muscle weakness
- Reduced ability of a muscle or group of muscles to produce force.
- Myasthenia gravis
- An autoimmune disorder that causes fluctuating muscle weakness, often affecting the eyes, face, and swallowing muscles.
- Myelin
- The insulating covering around many nerve fibers that helps electrical signals travel efficiently.
- Myelopathy
- Dysfunction of the spinal cord that can cause weakness, sensory changes, or problems with walking.
- Myocardial infarction
- Death of part of the heart muscle caused by inadequate blood flow, commonly called a heart attack.
- Myocarditis
- Inflammation of the heart muscle that can affect its pumping ability or electrical activity.
N
- Narcolepsy
- A neurological sleep disorder causing excessive daytime sleepiness and sometimes sudden loss of muscle tone.
- Nasal congestion
- A blocked or stuffy nose caused by swollen nasal tissues, mucus, or other obstruction.
- Nausea
- The unpleasant feeling of needing to vomit, which can occur with or without vomiting.
- Neck stiffness
- Difficulty moving the neck comfortably that may result from muscle strain, arthritis, or other conditions.
- Necrosis
- Death of cells or tissue from injury, disease, or inadequate blood supply, often triggering inflammation.
- Neoadjuvant therapy
- Treatment given before the main treatment, often to shrink a tumor or improve surgical options.
- Neonatal jaundice
- Yellowing of a newborn's skin or eyes due to elevated bilirubin, often temporary but sometimes needing treatment.
- Neonate
- A newborn baby during the first 28 days after birth.
- Neoplasm
- An abnormal growth of cells that may be benign or malignant.
- Nephron
- The microscopic functional unit of the kidney that filters blood and helps form urine.
- Nephrotic syndrome
- A kidney condition characterized by significant protein loss in urine, low blood protein, and swelling.
- Nerve conduction study
- A test measuring how quickly and strongly electrical signals travel through peripheral nerves.
- Neuralgia
- Pain occurring along a nerve, often described as sharp, burning, or electric-like.
- Neuron
- A nerve cell that receives and transmits information through electrical and chemical signals.
- Neuropathy
- Damage or dysfunction of nerves, which may cause numbness, tingling, pain, or weakness.
- Neuroplasticity
- The nervous system's ability to change its connections or functions in response to experience or injury.
- Neutrophil
- A white blood cell that is especially important for defending against many bacterial and fungal infections.
- Night sweats
- Episodes of marked sweating during sleep that can occur with infections, hormones, medicines, or other conditions.
- Non-heme iron
- A form of iron present in plant foods and many fortified foods whose absorption varies with the meal.
- NSAID
- A nonsteroidal anti-inflammatory drug used to relieve pain, inflammation, or fever.
- NT-proBNP test
- A blood test measuring a peptide released when the heart is under strain, often used in heart failure assessment.
- Nystagmus
- Involuntary rhythmic eye movements that may affect vision or balance.
O
- Obesity
- A chronic condition involving excess body fat that can affect health; BMI is one screening tool but not a complete assessment.
- Obstructive sleep apnea
- A sleep disorder in which the upper airway repeatedly narrows or closes during sleep, disrupting breathing.
- Occupational therapy
- Care that helps people develop or regain skills needed for everyday activities and independence.
- Odynophagia
- Pain associated with swallowing, which can occur with inflammation or injury of the throat or esophagus.
- Oliguria
- Lower-than-normal urine output, which may reflect dehydration, kidney problems, or other conditions.
- Omega-3 fatty acid
- A type of polyunsaturated fat involved in cell function; certain omega-3s are found in fish and plant foods.
- Omega-6 fatty acid
- A type of polyunsaturated fat required for normal cell structure and signaling.
- Open surgery
- An operation using a conventional incision to provide direct access to the treatment area.
- Opioid
- A class of substances that act on opioid receptors, including some prescription pain medicines and illicit drugs.
- Opportunistic infection
- An infection more likely to occur or become serious when the immune system is weakened.
- Optic nerve
- The nerve that carries visual information from the retina to the brain.
- Oral anticoagulant
- A medicine taken by mouth that reduces blood clot formation.
- Oral contraceptive
- A pill containing hormones or a progestin alone used to prevent pregnancy.
- Oral glucose tolerance test
- A blood sugar test measuring the response to a standardized glucose drink over time.
- Organ transplant
- Replacement of a failing organ with a healthy organ from a donor.
- Orthopnea
- Shortness of breath that worsens when lying flat and improves when sitting or standing.
- Orthostatic hypotension
- A drop in blood pressure after standing that may cause dizziness, weakness, or fainting.
- Osteoarthritis
- A joint disease involving changes to cartilage, bone, and other joint tissues that can cause pain and stiffness.
- Osteomyelitis
- An infection of bone that may cause localized pain, fever, or swelling.
- Osteoporosis
- A condition in which bones become less strong and more likely to fracture.
- Otitis externa
- Inflammation or infection of the outer ear canal, often called swimmer's ear.
- Otitis media
- Inflammation or infection of the middle ear, commonly occurring in children.
- Outbreak
- A localized rise in cases of a disease above the expected number.
- Ovarian cancer
- Cancer that begins in the ovary, fallopian tube, or nearby tissues, depending on its type.
- Ovary
- A reproductive organ that produces eggs and hormones such as estrogen and progesterone.
- Over-the-counter medicine
- A medicine that can be purchased without a prescription when used according to its label.
- Ovulation
- Release of an egg from an ovary during a menstrual cycle.
- Oxidative stress
- An imbalance between reactive molecules and the body's ability to control or repair their effects.
P
- Palliative care
- Specialized care that aims to relieve symptoms and stress associated with serious illness at any stage.
- Pallor
- Unusual paleness of the skin or mucous membranes, sometimes associated with anemia or reduced blood flow.
- Palpitations
- An awareness of the heartbeat that may feel racing, pounding, fluttering, or irregular.
- Pancreas
- An organ that produces digestive enzymes and hormones including insulin and glucagon.
- Pancreatic cancer
- Cancer that begins in the pancreas and may affect digestion or blood sugar regulation.
- Pancreatic enzyme
- An enzyme made by the pancreas that helps digest fats, proteins, or carbohydrates in the intestine.
- Pandemic
- An epidemic that spreads across multiple countries or continents and affects many people.
- Panic disorder
- A condition involving recurrent unexpected panic attacks and ongoing fear or behavioral changes related to attacks.
- Pap test
- A screening test collecting cervical cells to look for changes that may precede cervical cancer.
- Parathyroid gland
- One of the small glands near the thyroid that regulate blood calcium through parathyroid hormone.
- Parenteral nutrition
- Delivery of nutrients directly into a vein when the digestive tract cannot be used adequately.
- Paresthesia
- An abnormal skin sensation such as tingling, pins and needles, or burning without a clear external cause.
- Parkinson disease
- A progressive neurological disorder that commonly causes slowed movement, stiffness, and sometimes tremor.
- Passive immunity
- Temporary protection provided by antibodies received from another source rather than made by the person.
- Patella
- The kneecap, a bone in front of the knee joint that improves the leverage of the thigh muscles.
- Pathogen
- A microorganism or other biological agent capable of causing disease.
- Pathology
- The medical study of disease, including its causes and effects on cells, tissues, and organs.
- Pathophysiology
- The study of how disease disrupts the body's normal functions and processes.
- PCR test
- A laboratory method that amplifies selected DNA sequences to help detect genetic material from organisms or cells.
- Peak expiratory flow
- The fastest airflow a person can produce during a forceful breath out, often used in asthma monitoring.
- Pelvic floor
- A group of muscles and connective tissues supporting pelvic organs and helping control urination and bowel movements.
- Pelvic inflammatory disease
- Infection and inflammation of the upper female reproductive organs that may follow certain sexually transmitted infections.
- Penicillin antibiotic
- A family of antibiotics that treat susceptible bacteria by interfering with bacterial cell-wall formation.
- Peptic ulcer disease
- Open sores in the stomach or upper small intestine, commonly related to H. pylori or certain pain medicines.
- Percutaneous coronary intervention
- A catheter-based procedure used to open narrowed or blocked arteries supplying the heart.
- Pericardial effusion
- An abnormal buildup of fluid in the sac surrounding the heart.
- Pericarditis
- Inflammation of the sac surrounding the heart, sometimes causing sharp chest pain.
- Perimenopause
- The transition leading up to menopause, when menstrual patterns and hormone levels may fluctuate.
- Peripheral artery disease
- Reduced blood flow to the limbs from narrowing of arteries, usually caused by atherosclerosis.
- Peripheral nervous system
- The nerves outside the brain and spinal cord that connect the central nervous system with the body.
- Peripheral neuropathy
- Damage to nerves outside the brain and spinal cord, causing symptoms such as numbness, pain, or weakness.
- Peritoneal dialysis
- A treatment that uses the lining of the abdomen as a filter to remove waste and extra fluid.
- Pernicious anemia
- An autoimmune condition that impairs vitamin B12 absorption, potentially causing anemia and neurological symptoms.
- PET scan
- An imaging test using a small amount of radioactive tracer to show metabolic or other biological activity in tissues.
- Petechiae
- Tiny red or purple spots caused by bleeding from small blood vessels into the skin.
- Pharmacodynamics
- The study of how a drug affects the body, including its mechanisms and concentration-related effects.
- Pharmacokinetics
- The study of how a drug is absorbed, distributed, metabolized, and removed from the body.
- Phenotype
- The observable characteristics of a person or organism resulting from genes and environmental influences.
- Phosphate blood test
- A laboratory measurement of phosphate, a mineral involved in bones, energy production, and cell function.
- Phosphorus
- A mineral important for bones, cell membranes, and energy-related chemical reactions.
- Photophobia
- Discomfort or pain in response to light, sometimes associated with migraine or eye inflammation.
- Physical therapy
- Treatment using exercise, movement training, and other methods to improve function and mobility.
- Pituitary gland
- A small gland beneath the brain that releases hormones controlling growth, reproduction, and several other glands.
- Placebo
- An inactive treatment used in some clinical studies to help compare effects with an active intervention.
- Placebo effect
- A change in symptoms related to expectations and treatment context rather than the treatment's specific active mechanism.
- Placenta
- An organ developing during pregnancy that exchanges oxygen, nutrients, and wastes between parent and fetus.
- Placenta previa
- A placenta that covers or lies close to the cervical opening and can cause bleeding during pregnancy.
- Platelet
- A small blood cell fragment that helps form clots and limit bleeding.
- Platelet count
- A complete blood count measurement of the number of platelets circulating in blood.
- Pleura
- The thin membranes covering the lungs and lining the inside of the chest.
- Pleuritic chest pain
- Sharp chest pain that becomes worse with deep breathing or coughing.
- Pneumonia
- An infection or inflammation affecting lung air sacs that can cause cough, fever, and breathing difficulty.
- Polycystic ovary syndrome
- A hormonal and metabolic condition associated with irregular ovulation, androgen excess, and sometimes polycystic ovaries.
- Polymyalgia rheumatica
- An inflammatory condition causing aching and morning stiffness around the shoulders and hips, usually in older adults.
- Polyunsaturated fat
- A type of fat containing fatty acids with multiple double bonds, found in nuts, seeds, and many oils.
- Polyuria
- Production of an unusually large volume of urine, which may occur with diabetes or other conditions.
- Postnasal drip
- The sensation of mucus draining from the nose or sinuses into the throat.
- Postoperative care
- Monitoring and treatment given after surgery to support recovery and detect complications.
- Postpartum depression
- A depressive disorder occurring during or after pregnancy that affects mood, functioning, or bonding.
- Postpartum hemorrhage
- Excessive bleeding after childbirth that requires prompt medical assessment and treatment.
- Potassium
- An essential mineral and electrolyte involved in nerve signaling, muscle contraction, and fluid balance.
- Potassium blood test
- A laboratory measurement of potassium, an electrolyte important for muscles, nerves, and heart rhythm.
- Prebiotic
- A substance used by beneficial microorganisms in the body that can produce a health benefit.
- Prediabetes
- Blood glucose levels higher than normal but not high enough to meet the diagnostic criteria for diabetes.
- Preeclampsia
- A pregnancy-related condition involving new high blood pressure and signs of organ involvement, typically after 20 weeks.
- Premature atrial contraction
- An early heartbeat that begins in the upper chamber of the heart.
- Premature birth
- Birth before 37 completed weeks of pregnancy, associated with increased risk of newborn complications.
- Premature ventricular contraction
- An extra heartbeat originating in the lower chamber of the heart.
- Prenatal care
- Routine health care during pregnancy to monitor and support the pregnant person and developing baby.
- Prenatal ultrasound
- A sound-wave examination used during pregnancy to assess the fetus and pregnancy structures.
- Prescription medicine
- A medicine that legally requires authorization from a qualified health professional before dispensing.
- Prevalence
- The proportion of a population living with a particular disease or condition at a given time or during a period.
- Preventive care
- Health services intended to reduce the risk of disease or identify problems before symptoms develop.
- Primary amenorrhea
- Absence of the first menstrual period by an age when menstruation would normally be expected.
- Probiotic
- A live microorganism that may provide a health benefit when taken in adequate amounts for a specific purpose.
- Procalcitonin test
- A blood test measuring a protein that may rise with certain bacterial infections and systemic inflammation.
- Progesterone
- A hormone involved in regulating the menstrual cycle and supporting pregnancy.
- Prognosis
- The expected course or likely outcome of a disease or health condition.
- Prolactin
- A hormone produced by the pituitary gland that stimulates milk production and affects reproductive hormones.
- Prophylaxis
- An action or treatment intended to prevent a disease or complication.
- Prostate
- A gland below the bladder that contributes fluid to semen and surrounds part of the urethra.
- Prostate-specific antigen test
- A blood test measuring PSA, which can rise with prostate cancer and several noncancerous prostate conditions.
- Prosthesis
- An artificial device that replaces a missing body part or supports a body function.
- Protein
- A nutrient made from amino acids that supports tissues, enzymes, hormones, and immune functions.
- Proteinuria
- An abnormal amount of protein in urine that may be a sign of kidney disease.
- Prothrombin time
- A blood clotting test that measures how long plasma takes to form a clot through specific pathways.
- Proton pump inhibitor
- A medicine that reduces stomach acid production by blocking acid-producing pumps in stomach cells.
- Pruritus
- The medical term for itching, which may occur with skin or systemic conditions.
- Psoriasis
- A chronic immune-mediated skin disease that often causes thick, scaly, inflamed patches.
- Psoriatic arthritis
- Inflammatory arthritis associated with psoriasis that can affect joints, tendons, and the spine.
- Ptosis
- Drooping of an upper eyelid, which can occur with muscle, nerve, or eyelid disorders.
- Pulmonary artery
- An artery carrying blood from the right side of the heart to the lungs for oxygenation.
- Pulmonary embolism
- A blood clot or other blockage in an artery of the lung, potentially causing sudden breathing problems.
- Pulmonary hypertension
- High blood pressure in the arteries of the lungs, which can strain the right side of the heart.
- Pulmonary vein
- A vein carrying oxygenated blood from the lungs back to the left atrium.
- Pulse oximetry
- A noninvasive method of estimating blood oxygen saturation using a sensor placed on a finger or other site.
- Pupil
- The adjustable opening in the center of the iris that controls how much light enters the eye.
- Purpura
- Purple or reddish spots or patches caused by bleeding under the skin.
R
- Radiation therapy
- Treatment using high-energy radiation to damage or destroy targeted cells, commonly cancer cells.
- Radiculopathy
- Symptoms caused by irritation or compression of a spinal nerve root, potentially producing pain or weakness.
- Rapid antigen test
- A test that detects specific proteins from a germ, often providing results faster than laboratory molecular tests.
- Rapid-acting insulin
- An insulin preparation that begins working quickly and is commonly used around meals.
- Receptor agonist
- A substance that binds to and activates a receptor to produce a biological response.
- Receptor antagonist
- A substance that binds to a receptor and prevents or reduces its activation.
- Rectum
- The final portion of the large intestine, which temporarily stores stool before a bowel movement.
- Recurrence
- The return of a disease or symptom after a period of improvement or apparent absence.
- Red blood cell count
- A laboratory measurement of the number of red blood cells in a blood sample.
- Rehabilitation
- Care and therapy designed to help a person regain or improve function after illness, injury, or disability.
- Relapse
- A return or worsening of disease after a period of improvement or remission.
- Remission
- A period when signs or symptoms of a disease decrease significantly or disappear, though the condition may return.
- Resting heart rate
- The number of heartbeats per minute when a person is awake, calm, and physically at rest.
- Restless legs symptoms
- An uncomfortable urge to move the legs, usually worse during rest and often relieved by movement.
- Resuscitation
- Emergency measures intended to restore or maintain breathing and circulation.
- Reticulocyte count
- A blood test measuring young red blood cells to help evaluate bone marrow response to anemia.
- Retina
- The light-sensitive tissue at the back of the eye that converts light into nerve signals.
- Rheumatoid arthritis
- An autoimmune inflammatory arthritis that commonly affects the small joints of the hands and feet.
- Rheumatoid factor test
- A blood test for an antibody that can be present in rheumatoid arthritis and other conditions.
- Rhinorrhea
- A runny nose caused by excess nasal fluid, often associated with infection or allergies.
- Right ventricle
- The heart chamber that pumps blood through the pulmonary artery to the lungs.
- Rigidity
- Increased resistance to passive movement of a muscle or joint, sometimes linked to neurological disorders.
- Risk factor
- A characteristic or exposure associated with a greater chance of developing a particular condition.
- Rosacea
- A chronic inflammatory facial skin condition that can cause flushing, redness, and acne-like bumps.
S
- Sacrum
- The triangular bone at the base of the spine that joins the spine to the pelvis.
- Sarcoidosis
- An inflammatory disease involving clusters of immune cells called granulomas, often affecting the lungs and lymph nodes.
- Saturated fat
- A type of dietary fat without double bonds in its fatty acid chains, found in animal and some tropical plant foods.
- Scapula
- The shoulder blade, a flat bone supporting shoulder movement and muscle attachment.
- Sciatica
- Pain traveling along the path of the sciatic nerve, often from the lower back into one leg.
- Sclera
- The tough white outer coat of the eye that protects it and helps maintain its shape.
- Scleroderma
- A group of autoimmune diseases that can cause skin thickening and, in systemic forms, affect internal organs.
- Second trimester
- The middle stage of pregnancy, commonly from 14 through 27 completed weeks.
- Secondary amenorrhea
- The stopping of menstrual periods in someone who previously menstruated.
- Sedation
- Use of medication to reduce awareness, anxiety, or discomfort during a medical procedure.
- Seizure
- A sudden episode of abnormal brain electrical activity that may alter movement, sensation, awareness, or behavior.
- Selective serotonin reuptake inhibitor
- An antidepressant class that increases serotonin signaling by reducing its reuptake into nerve cells.
- Selenium
- A trace mineral needed for antioxidant enzymes, thyroid hormone metabolism, and other functions.
- Sensitivity
- In diagnostic testing, the proportion of people with a condition who correctly test positive.
- Sepsis
- A life-threatening condition caused by the body's extreme response to an infection, leading to organ dysfunction.
- Serum osmolality
- A measurement of the concentration of dissolved particles in blood, useful in fluid and sodium disorders.
- Serum sodium test
- A laboratory measurement of sodium concentration in the blood, essential for assessing fluid and electrolyte balance.
- SGLT2 inhibitor
- A medicine that lowers blood glucose by increasing glucose loss through urine and may also benefit certain heart or kidney conditions.
- Shingles
- A painful blistering rash caused by reactivation of the varicella-zoster virus after chickenpox.
- Sickle cell disease
- A group of inherited blood disorders in which abnormal hemoglobin can cause red blood cells to become rigid and obstruct circulation.
- Side effect
- An unintended effect of a medicine or treatment that occurs in addition to its intended effect.
- Sinusitis
- Inflammation of the sinuses that can cause nasal congestion, facial pressure, or thick nasal discharge.
- Sleep apnea
- A disorder involving repeated pauses or reductions in breathing during sleep.
- Sleep paralysis
- A temporary inability to move or speak while falling asleep or waking up, despite being conscious.
- Small intestine
- The long digestive tube where most nutrient digestion and absorption take place.
- Sodium
- An essential electrolyte that helps regulate fluid balance and supports nerve and muscle activity.
- Soluble fiber
- Dietary fiber that dissolves or swells in water and can help with stool consistency or cholesterol management.
- Sore throat
- Pain, irritation, or scratchiness in the throat that commonly occurs with viral infections.
- Spastic paresis
- Weakness combined with increased muscle tone caused by damage to upper motor neuron pathways.
- Spasticity
- Increased muscle tone that causes stiffness and resistance to movement, often after injury to the central nervous system.
- Specificity
- In diagnostic testing, the proportion of people without a condition who correctly test negative.
- Spinal cord
- A bundle of nerve tissue inside the spine that carries signals between the brain and body.
- Spinal muscular atrophy
- An inherited motor-neuron disorder causing progressive muscle weakness and wasting.
- Spinal stenosis
- Narrowing of spaces in the spine that can compress nerves and cause pain, numbness, or weakness.
- Spirometry
- A breathing test that measures how much air a person can exhale and how quickly it is exhaled.
- Spleen
- An organ that filters blood, removes old blood cells, and helps the immune system respond to infections.
- Sporadic
- Occurring occasionally or irregularly rather than in a persistent or inherited pattern.
- Stable angina
- Predictable chest discomfort from reduced blood flow to the heart, often triggered by exertion and relieved by rest.
- Statin
- A medicine that lowers LDL cholesterol by reducing cholesterol production in the liver.
- Status epilepticus
- A prolonged seizure or repeated seizures without recovery between them that require emergency treatment.
- Stent
- A small tube or mesh device placed inside a narrowed passage, commonly a blood vessel, to keep it open.
- Sterilization
- A method that permanently prevents reproduction or a process that eliminates microorganisms from equipment.
- Sternum
- The breastbone at the front of the chest, connected to ribs by cartilage.
- Stillbirth
- Delivery of a baby without signs of life at or after a gestational age defined by the applicable health system.
- Stool culture
- A laboratory test that checks a stool sample for certain infectious bacteria.
- Strep throat
- A throat infection caused by group A Streptococcus bacteria, often causing fever and painful swallowing.
- Stress echocardiogram
- An ultrasound examination of heart function performed during or after exercise or medication-induced stress.
- Stridor
- A harsh, high-pitched breathing sound caused by narrowing of the upper airway.
- Stroke
- Sudden brain injury caused by interrupted blood supply or bleeding in the brain; it is a medical emergency.
- Stroke volume
- The amount of blood ejected from one ventricle during a single heartbeat.
- Subarachnoid hemorrhage
- Bleeding into the space surrounding the brain, sometimes caused by a ruptured aneurysm.
- Subcutaneous injection
- Administration of medicine into the fatty tissue just below the skin.
- Subdural hematoma
- A collection of blood between the dura and brain surface, often after head trauma.
- Supraventricular tachycardia
- A rapid heart rhythm originating above the ventricles or involving the upper part of the heart's conduction system.
- Surveillance
- Systematic monitoring of health events or a person's condition to identify changes needing action.
- Suture
- A stitch or thread used to close a cut or surgical incision.
- Sympathetic nervous system
- The branch of the autonomic nervous system that helps prepare the body for stress or physical activity.
- Syncope
- A brief loss of consciousness due to a temporary drop in blood flow to the brain.
- Synovial fluid
- A lubricating fluid within many joints that helps reduce friction during movement.
- Systemic lupus erythematosus
- An autoimmune disease that can involve the skin, joints, kidneys, blood, and other organs.
- Systolic pressure
- The upper blood pressure number, representing pressure in the arteries when the heart contracts.
T
- T cell
- A type of lymphocyte involved in coordinating immune responses and destroying certain infected or abnormal cells.
- Tachycardia
- A heart rate that is faster than expected for a person's age or situation.
- Targeted therapy
- Treatment designed to interfere with specific molecules or pathways involved in a disease, especially cancer.
- Tendinitis
- Irritation or inflammation of a tendon, the strong tissue that connects muscle to bone.
- Tendon
- Strong connective tissue that attaches a muscle to a bone.
- Tension-type headache
- A common headache disorder that usually causes pressing or tightening pain without prominent nausea.
- Testicle
- A male reproductive organ that produces sperm and testosterone.
- Thalamus
- A brain structure that relays many sensory and motor signals to the cerebral cortex.
- Therapeutic index
- A measure comparing amounts of a drug that cause desired effects with amounts that cause harmful effects.
- Thiazide diuretic
- A medicine that increases salt and water excretion in the kidneys, commonly used for high blood pressure.
- Third trimester
- The final stage of pregnancy, generally starting at 28 weeks and continuing until delivery.
- Throat culture
- A laboratory test that checks a throat swab for certain bacteria, including group A streptococci.
- Thrombectomy
- A procedure to physically remove a blood clot from a vessel.
- Thrombocytopenia
- A lower-than-normal platelet count that can increase bleeding risk, depending on its severity and cause.
- Thrombolysis
- Treatment that dissolves a blood clot using medication.
- Thrombosis
- Formation of a blood clot inside a blood vessel, which can partially or completely block blood flow.
- Thyroid gland
- A gland in the neck that produces hormones regulating metabolism and many body functions.
- Thyroid hormone replacement
- Medicine that supplies thyroid hormone when the thyroid gland does not produce enough.
- Thyroid stimulating hormone test
- A blood test measuring TSH, a hormone used to assess how the thyroid gland is functioning.
- Thyroiditis
- Inflammation of the thyroid gland that can cause changes in thyroid hormone levels.
- Tibia
- The larger shinbone of the lower leg that bears much of the body's weight.
- Tinnitus
- Hearing a ringing, buzzing, or other sound without a corresponding external source.
- Tissue graft
- Transfer of tissue from one site or donor to repair or replace damaged tissue elsewhere.
- Topical medicine
- A medicine applied directly to the skin or another body surface, often for a local effect.
- Trachea
- The windpipe, carrying inhaled air from the voice box toward the bronchi.
- Tracheostomy
- A surgically created opening in the neck into the trachea to help with breathing or airway care.
- Trans fat
- A type of unsaturated fat with a trans chemical structure, some forms of which increase cardiovascular risk.
- Transferrin saturation
- A calculated percentage showing how much of the blood's iron-transport protein is carrying iron.
- Transient ischemic attack
- A temporary episode of neurological symptoms caused by reduced blood flow to the brain without an acute infarction.
- Transmission
- The process by which an infectious agent passes between people, animals, or other sources.
- Tremor
- An involuntary rhythmic shaking movement of a body part.
- Trigeminal neuralgia
- A nerve pain disorder causing brief, severe, electric shock-like facial pain.
- Triglyceride
- A fat molecule that serves as a major form of energy storage in the body and circulates in blood.
- Triglyceride test
- A blood measurement of circulating triglycerides, one type of fat used in cardiovascular risk assessment.
- Troponin test
- A blood test measuring heart muscle proteins that rise when heart cells are injured.
- Tuberculosis
- An infection caused by Mycobacterium tuberculosis that usually affects the lungs but can involve other organs.
U
- Ulcer
- An open sore in the skin or a body lining, such as the stomach or intestine.
- Ulcerative colitis
- An inflammatory bowel disease causing continuous inflammation of the colon lining, starting in the rectum.
- Ultrasound-guided biopsy
- A procedure using real-time sound-wave images to guide a needle into tissue for sampling.
- Umbilical cord
- The structure connecting a fetus to the placenta, carrying blood for oxygen and nutrient exchange.
- Unintentional weight loss
- A decrease in body weight without deliberate dieting or increased activity, sometimes indicating illness.
- Ureter
- A tube that carries urine from a kidney to the urinary bladder.
- Urethra
- The tube that carries urine from the bladder to the outside of the body.
- Urinalysis
- A set of tests examining urine for substances, cells, and other findings that may suggest medical conditions.
- Urinary incontinence
- Unintentional leakage of urine, which may occur with exertion, urgency, or other circumstances.
- Urinary tract infection
- An infection affecting part of the urinary system, often the bladder, that may cause burning or frequent urination.
- Urinary urgency
- A sudden, difficult-to-delay need to urinate, sometimes associated with bladder conditions.
- Urine albumin-creatinine ratio
- A urine test comparing albumin with creatinine to help detect and monitor kidney damage.
- Urine culture
- A laboratory test used to identify bacteria or fungi growing in urine when infection is suspected.
- Uterine prolapse
- Descent of the uterus into the vagina due to weakened pelvic support tissues.
- Uterus
- The muscular reproductive organ in which a pregnancy can develop.
V
- Vaccination
- Administration of a vaccine to train the immune system to recognize a particular infectious threat.
- Vaccine adjuvant
- A substance included in some vaccines to help strengthen the immune response.
- Vagina
- The muscular canal connecting the cervix to the outside of the body.
- Vaginal delivery
- Childbirth in which the baby passes through the vagina rather than being delivered by cesarean surgery.
- Varicose veins
- Enlarged, twisted superficial veins caused by weakened vein valves and impaired blood flow.
- Vasculitis
- Inflammation of blood vessel walls that can reduce blood flow or damage tissues.
- Vasodilator
- A medicine or substance that widens blood vessels and can improve blood flow or lower blood pressure.
- Vasopressor
- A medicine used to raise dangerously low blood pressure, often by narrowing blood vessels.
- Vector
- A living carrier, such as a mosquito or tick, that can transmit an infectious agent.
- Vein
- A blood vessel that returns blood toward the heart, often with valves that help prevent backflow.
- Ventilator weaning
- A gradual process of reducing mechanical breathing support when a person can increasingly breathe independently.
- Ventricle
- One of the two lower chambers of the heart that pumps blood out of the heart.
- Ventricular fibrillation
- A dangerous heart rhythm with disorganized ventricular activity that prevents effective pumping.
- Ventricular tachycardia
- A fast abnormal rhythm originating in the ventricles that can impair circulation.
- Vertebra
- One of the bones forming the spinal column and protecting the spinal cord.
- Vertigo
- A false sensation that you or your surroundings are spinning or moving.
- Vestibular neuritis
- Inflammation or dysfunction of a balance nerve that can cause sudden severe vertigo.
- Viral load
- The measured amount of viral genetic material or virus in a sample, often used to monitor infections.
- Virus
- An infectious agent that requires living cells to reproduce and may cause a range of diseases.
- Vitamin A
- A fat-soluble vitamin needed for vision, immune function, and normal tissue maintenance.
- Vitamin B1
- Also called thiamine, a water-soluble vitamin involved in energy metabolism and nerve function.
- Vitamin B12 deficiency
- A shortage of vitamin B12 that can lead to anemia and neurological problems such as numbness or tingling.
- Vitamin B12 test
- A blood test measuring vitamin B12, often used when investigating anemia or nerve symptoms.
- Vitamin B2
- Also called riboflavin, a vitamin involved in reactions that help cells use energy.
- Vitamin B3
- Also called niacin, a vitamin needed to make coenzymes involved in energy metabolism.
- Vitamin B6
- A vitamin involved in amino acid metabolism, brain signaling, and hemoglobin production.
- Vitamin B9
- Also called folate, a vitamin needed for DNA synthesis and red blood cell formation.
- Vitamin C
- A water-soluble vitamin needed for collagen production and antioxidant functions.
- Vitamin D test
- A blood test usually measuring 25-hydroxyvitamin D to evaluate vitamin D status.
- Vitamin E
- A fat-soluble vitamin that helps protect cell membranes from oxidative damage.
- Vitamin K
- A fat-soluble vitamin required for normal blood clotting and involved in bone proteins.
- Vitiligo
- A condition in which areas of skin lose pigment because pigment-producing cells are damaged or absent.
- Vocal cords
- Two bands of tissue in the larynx that vibrate to produce voice.
- Von Willebrand disease
- A common inherited bleeding disorder involving reduced amount or function of von Willebrand factor.
- Vulvovaginal candidiasis
- A yeast infection affecting the vulva or vagina, often causing itching and irritation.
W
- Warfarin
- An oral anticoagulant that limits vitamin K-dependent clotting factors and requires INR monitoring.
- Water-soluble vitamin
- A vitamin that dissolves in water, including vitamin C and the B vitamins.
- Wernicke encephalopathy
- A neurological emergency caused by thiamine deficiency that may affect balance, eye movements, and thinking.
- Wheezing
- A whistling sound during breathing caused by narrowing or obstruction of airways.
- White blood cell
- A cell of the immune system that helps defend the body against infection and other threats.
- White blood cell differential
- A blood test showing the amounts or proportions of different types of white blood cells.
- Whooping cough
- A contagious respiratory infection caused by Bordetella pertussis, sometimes producing prolonged coughing spells.
- Wilson disease
- An inherited disorder in which copper builds up in the liver, brain, and other tissues.
- Wound dressing
- A covering applied to a wound to protect it, absorb drainage, or support healing.
- Wound irrigation
- Rinsing a wound with suitable fluid to remove debris and reduce contamination.
X
- Xerostomia
- The medical term for dry mouth caused by reduced saliva production or an altered sensation of dryness.
Z
- Zika virus infection
- A mosquito-borne viral infection that can cause mild symptoms but may harm a developing fetus during pregnancy.
- Zinc
- An essential mineral involved in immune function, wound healing, growth, and many enzyme reactions.
- Zoonosis
- An infectious disease that can be transmitted between animals and humans.
No matching medical terms found. Try another search.
This dictionary is for general health education and is not a substitute for professional medical advice.