Medical glossary

Jump to a letter: A · B · C · D · E · F · G · H · I · J · L · M · N · O · P · R · S · T · U · V · W · X

A

Abscess

A pocket of pus walled off inside the body, caused by a bacterial infection. Many need to be drained. See abscess.

Acute

Starting suddenly or lasting a short time, such as acute bronchitis. It describes timing, not severity.

Anaphylaxis

A severe, whole-body allergic reaction that can block the airway and drop blood pressure within minutes. It is treated with epinephrine and is always an emergency. See anaphylaxis.

Anemia

Having too few healthy red blood cells or too little hemoglobin, so less oxygen reaches the tissues. It often causes tiredness and pale skin. See anemia.

Aneurysm

A weak spot in a blood vessel wall that bulges outward like a balloon. A burst aneurysm causes severe internal bleeding. See aortic aneurysm.

Angina

Chest pain or pressure caused by too little blood flow to the heart muscle, usually brought on by exertion and eased by rest. See angina.

Antibiotic

A medicine that kills bacteria or stops them from growing. Antibiotics do not work against viruses such as colds and flu.

Antibody

A protein made by the immune system that recognizes and helps destroy a specific germ or foreign substance. Blood tests for antibodies can show past infection or vaccination.

Anticoagulant

A medicine that slows blood clotting, often called a blood thinner. It is used to prevent and treat clots and raises the risk of bleeding.

Antihistamine

A medicine that blocks histamine, a chemical released in allergic reactions. It eases itching, sneezing and hives, and older types cause drowsiness.

Aphasia

Difficulty speaking, understanding, reading or writing language, usually after damage to the brain such as a stroke. See aphasia.

Arrhythmia

An abnormal heart rhythm: too fast, too slow or irregular. See arrhythmia.

Arthralgia

Pain in a joint, without necessarily any swelling. See joint pain.

Ataxia

Poor coordination of movement, causing an unsteady walk, clumsy hands or slurred speech. See ataxia.

B

Benign

Not cancerous and not spreading to other parts of the body. A benign growth can still cause problems if it presses on nearby structures.

Biopsy

Removing a small sample of tissue so it can be examined under a microscope. It is the main way to confirm or rule out cancer.

Bradycardia

A slow heart rate, usually under 60 beats a minute at rest in adults. It is normal in many fit people. See bradycardia.

Bronchitis

Inflammation of the main airways in the lungs, causing a cough that often brings up mucus. See acute bronchitis.

C

Cardiac arrest

When the heart suddenly stops pumping effectively, so the person collapses and stops breathing normally. It needs CPR and a defibrillator within minutes. See cardiac arrest.

Cellulitis

A bacterial infection of the deeper layers of the skin, causing a spreading area of red, warm, swollen and tender skin. See cellulitis.

Chronic

Lasting a long time, usually more than 3 months, or coming back again and again. Like "acute", it describes timing, not severity.

Comorbidity

Another illness a person has at the same time as the main condition, such as diabetes in someone with heart disease.

Contraindication

A reason not to use a particular treatment, because it could be harmful. For example, a stomach ulcer is a contraindication to ibuprofen.

CT scan

Computed tomography: a scan that uses X-rays and a computer to make detailed cross-section pictures of the body. It is fast and widely used in emergencies.

Cyanosis

A blue or gray tinge to the lips, skin or nail beds, caused by low oxygen in the blood. New cyanosis is an emergency.

D

Dehydration

Losing more fluid than you take in, so the body lacks the water it needs. Signs include thirst, dark urine and dizziness. See dehydration.

Dermatitis

Inflammation of the skin, causing redness, itching and sometimes blistering or flaking. Eczema is a common type. See dermatitis.

Diagnosis

The identification of the disease or condition causing a person's symptoms.

Differential diagnosis

The list of possible conditions that could explain a set of symptoms, which a doctor narrows down with questions, an exam and tests.

Dysphagia

Difficulty swallowing, or a feeling that food sticks on the way down. See difficulty swallowing.

Dyspnea

Shortness of breath, or the feeling of not getting enough air. See dyspnea.

Dysuria

Pain, burning or discomfort when passing urine, often from a urinary tract infection. See painful urination.

E

ECG

Electrocardiogram (also EKG): a quick, painless test that records the heart's electrical activity using stickers on the chest. It helps detect heart attacks and rhythm problems.

Edema

Swelling caused by fluid trapped in the body's tissues, most often in the feet, ankles and legs. See edema.

Embolism

A blockage in a blood vessel caused by material carried in the bloodstream, usually a blood clot. See pulmonary embolism.

Endoscopy

Looking inside the body with a thin, flexible tube that has a light and camera on the end. Colonoscopy is a type of endoscopy.

Epinephrine

Also called adrenaline: a hormone and medicine that opens the airways and raises blood pressure. An epinephrine auto-injector is the first treatment for anaphylaxis.

Etiology

The cause or origin of a disease.

F

Febrile

Having a fever. A febrile seizure is a seizure in a young child caused by a fever.

Fever

A body temperature of 38 °C (100.4 °F) or higher, usually a sign the body is fighting an infection. See fever.

Fracture

A broken bone, from a hairline crack to a complete break. See bone fracture.

G

Gastritis

Inflammation of the stomach lining, causing upper belly pain, nausea or indigestion. See gastritis.

Generic drug

A medicine with the same active ingredient, strength and effect as a brand-name drug, usually sold at a lower price.

GERD

Gastroesophageal reflux disease: frequent backflow of stomach acid into the esophagus (food pipe), causing heartburn. See GERD.

H

Hematemesis

Vomiting blood, which may look bright red or like coffee grounds. It needs emergency care. See vomiting blood.

Hematuria

Blood in the urine, either visible or found only on a test. See hematuria.

Hemoglobin

The iron-containing protein in red blood cells that carries oxygen. A low level means anemia.

Hemoptysis

Coughing up blood or blood-streaked mucus from the lungs. See hemoptysis.

Hernia

When an organ or fatty tissue pushes through a weak spot in the muscle wall that holds it in, often making a bulge in the groin or belly. See hernia.

Hives

Raised, itchy welts on the skin that come and go, often from an allergy. The medical name is urticaria. See hives.

Hypertension

High blood pressure: pressure in the arteries that stays at or above 130/80 mm Hg by current US guidelines. It usually causes no symptoms. See high blood pressure.

Hypoglycemia

Low blood sugar, usually below 70 mg/dL (3.9 mmol/L). It causes shakiness, sweating and confusion, and is most common in people treated for diabetes. See hypoglycemia.

Hypotension

Low blood pressure. It is often harmless but can cause dizziness or fainting. See hypotension.

Hypoxia

Too little oxygen reaching the body's tissues. It can cause breathlessness, confusion and a blue tinge to the skin.

I

Idiopathic

Having no known cause.

Immunocompromised

Having a weakened immune system, from a disease or from medicines such as chemotherapy or steroids, so infections are more likely and can be more serious.

Infection

Invasion of the body by germs such as bacteria, viruses, fungi or parasites that multiply and cause illness. See infection.

Inflammation

The body's response to injury or infection, causing redness, heat, swelling and pain. Long-lasting inflammation can damage tissue.

Insomnia

Trouble falling asleep, staying asleep, or waking too early, at least 3 nights a week. See insomnia.

Ischemia

Reduced blood flow to a part of the body, starving it of oxygen. Ischemia of the heart causes angina; prolonged ischemia causes tissue death.

J

Jaundice

Yellowing of the skin and the whites of the eyes, caused by a buildup of bilirubin, a pigment the liver normally clears. See jaundice.

L

Lesion

Any abnormal area of tissue, such as a sore, lump, patch or spot. The word does not say whether it is harmless or serious.

Lethargy

Abnormal drowsiness, sluggishness or lack of energy. See lethargy.

Lymph nodes

Small, bean-shaped glands in the neck, armpits, groin and elsewhere that filter fluid and help fight infection. They swell during infections. See swollen lymph nodes.

M

Malaise

A general feeling of being unwell, uncomfortable or "off", without one specific symptom.

Malignant

Cancerous: able to invade nearby tissue and spread to other parts of the body. See cancer.

Melena

Black, sticky, tar-like stools caused by bleeding high in the digestive tract. See melena.

Metastasis

Spread of cancer from where it started to another part of the body. See metastatic cancer.

MRI

Magnetic resonance imaging: a scan that uses a strong magnet and radio waves, not X-rays, to make detailed pictures, especially of the brain, spine and joints.

Myalgia

Muscle pain or aching. See muscle pain.

N

Nausea

An uneasy feeling in the stomach with an urge to vomit. See nausea.

Necrosis

Death of body tissue, usually from loss of blood supply, infection or injury.

Neuralgia

Sharp, shooting or burning pain along the path of a nerve. See neuralgia.

Neuropathy

Damage to nerves, often causing numbness, tingling or burning in the feet and hands. Diabetes is a common cause. See peripheral neuropathy.

Nocturia

Waking up at night one or more times to pass urine. See nocturia.

NSAID

Nonsteroidal anti-inflammatory drug: a group of pain relievers that also reduce inflammation, including ibuprofen, naproxen and aspirin. See medication safety.

O

Orthopnea

Shortness of breath when lying flat that eases on sitting up. It can be a sign of heart failure.

OTC

Over the counter: medicines you can buy without a prescription.

Otitis media

Infection or inflammation of the middle ear, behind the eardrum, common in young children. See otitis media.

P

Palliative care

Care focused on relieving symptoms and improving quality of life in serious illness. It can be given alongside treatment aimed at a cure.

Palpitations

Being aware of your own heartbeat: pounding, fluttering, racing or skipped beats. See heart palpitations.

Paresthesia

Tingling, prickling or "pins and needles" in the skin. See paresthesia.

Pathogen

Any germ that can cause disease, such as a bacterium, virus, fungus or parasite.

Prognosis

The likely course and outcome of a disease, including the chance of recovery.

Prophylaxis

Treatment given to prevent a disease rather than to treat it, such as a vaccine or antibiotics before some surgery.

Pruritus

Itching. See pruritus.

Pulse oximeter

A small clip on the finger that estimates the oxygen level in the blood. Normal readings are usually 95% to 100%. Readings can be less accurate on darker skin.

R

Referred pain

Pain felt in a different place from its source. For example, a heart attack can cause pain in the jaw or arm.

Remission

A period when the signs and symptoms of a disease lessen or disappear. It may be partial or complete.

Rhinorrhea

A runny nose. See runny nose.

S

Sepsis

A life-threatening reaction to an infection in which the body's response damages its own organs. See sepsis.

Sign

Something a doctor can observe or measure, such as a rash, a fever or a heart murmur. A symptom is something you feel and report, such as pain or nausea.

Stenosis

Abnormal narrowing of a passage in the body, such as a blood vessel, heart valve or the spinal canal. See aortic stenosis.

Stroke

Sudden loss of brain function caused by a blocked or burst blood vessel in the brain. It is a medical emergency. See stroke.

Syncope

Fainting: a brief loss of consciousness caused by a temporary drop in blood flow to the brain. See syncope.

Systemic

Affecting the whole body rather than one part.

T

Tachycardia

A fast heart rate, over 100 beats a minute at rest in adults. See tachycardia.

Thrombosis

A blood clot forming inside a blood vessel and blocking blood flow. See deep vein thrombosis.

TIA

Transient ischemic attack, or "mini-stroke": stroke symptoms that go away within minutes to hours. It is a warning sign and needs emergency assessment. See TIA.

Tinnitus

Hearing ringing, buzzing or hissing sounds that have no outside source. See tinnitus.

Triage

Sorting patients by how urgently they need care, so the sickest are seen first.

U

Ultrasound

A scan that uses sound waves to make pictures of organs, blood vessels or a baby in the womb. It uses no radiation.

Urticaria

The medical name for hives. See urticaria.

V

Vaccine

A preparation that trains the immune system to recognize a germ, so the body can fight it off faster in the future.

Vertigo

A false feeling that you or your surroundings are spinning or moving. It usually comes from the inner ear. See vertigo.

Virus

A tiny germ that can only multiply inside living cells. Viruses cause colds, flu and COVID-19, and antibiotics do not kill them.

Vital signs

Basic measurements of body function: temperature, pulse, breathing rate, blood pressure and often oxygen level.

W

Wheezing

A high-pitched whistling sound on breathing, caused by narrowed airways, as in asthma. See wheezing.

X

X-ray

A quick imaging test that uses a small dose of radiation to show bones and some organs, such as the lungs.

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