Medical terms A–Z

Built to stay out of the brain, it blunts allergy symptoms without the sedation that older antihistamines are known for.

Two kinds behave quite differently in the gut: one dissolves into a gel, the other keeps its structure and adds bulk.

Fiberoptic describes thin, flexible strands that transmit light and images, a technology behind many internal medical viewing instruments.

A fibroadenoma is a common, benign breast tumor made of fibrous and glandular tissue, most frequent in younger women.

The cell that builds the body's structural framework, and the same cell that closes a wound by making a scar.

Lumpiness, tenderness and cysts that shift with the monthly cycle, common enough to be considered a normal variation.

The older name for ordinary cyclical breast lumpiness, kept in many records although the word disease is now considered inaccurate.

A benign smooth-muscle tumor, usually in the uterus or gastrointestinal tract.

Growths that invade locally and return after removal yet never travel to distant organs, sitting between benign and malignant.

Pain here is generated by altered processing within the nervous system, which is a mechanism rather than the absence of one.

A diagnosis that has shrunk as laboratory testing improved, since most tumors once given the name proved to be something else.

Fibrosis is the buildup of dense scar-like tissue in an organ, which can stiffen it and interfere with its normal function over time.

Fibrous tissue is made up of dense strands of connective fiber, giving it strength and structure but comparatively little flexibility.

The main sensory nerve of the head and face, and the motor nerve of the muscles used in chewing.

A rare inherited condition in which one or more tumors form in the parathyroid glands (four pea-sized organs found on the thyroid) and cause them to make too much parathyroid hormone.

A drug used to increase numbers of white blood cells in patients who are receiving chemotherapy.

Filler most often refers to an inactive ingredient bulking a medication, but the term also describes an injectable substance used to add facial volume.

The use of x-rays to create a picture of the breast on a film.

The removal of tissue or fluid with a thin needle for examination under a microscope.

The closest ring of biological family, parents, siblings and children, who share about half their genes with a given person.

Initial treatment used to reduce a cancer.

An abnormal opening or passage between two organs or between an organ and the surface of the body.

An ancient form of acupuncture based on the principle that there are five universal elements (wood, fire, earth, metal, and water) that affect a person's emotions, personality, health, and response…

An antibiotic/antifungal drug used to treat infection.

A pigment family coloring much of the plant world, and the clearest example of test tube antioxidant power failing to transfer into a body.

A substance being studied in the treatment of several types of cancer.

A rhythm-control drug rather than a rate-control one, limited to hearts without structural disease because of a documented safety concern.

Its real value is that it forces every branch to be stated, including the choices a written paragraph can leave comfortably vague.

Flow cytometry rapidly measures thousands of individual cells as they stream past a laser, characterizing their size, internal structure, and surface markers.

A grid in the chart where the same measurement is written again and again, so a trend shows at a glance.

A drug that increases the number of immune cells and may stimulate the immune system to kill cancer cells.

A chemotherapy drug that impersonates a DNA building block, used mainly against slow-growing blood cancers and before transplant.

Salt handling rather than swelling: this is the steroid given for what the kidney does with sodium, and it rarely works alone.

Fluid refers to any substance, liquid or gas, that flows and conforms to the shape of its container.

A laboratory technique used to look at genes or chromosomes in cells and tissues.

Fluorescence microscopy uses light-emitting dyes or naturally fluorescent molecules to make specific cells, proteins, or organisms visible against a dark background.

Fluoride is a mineral that strengthens tooth enamel and helps prevent decay, delivered through water, toothpaste, and dental treatments.

One of a group of substances used to treat cancer.

Fluoroquinolones are broad spectrum antibiotics that stop bacteria from replicating their DNA, used against a range of respiratory and urinary infections.

A fluoroscope is the imaging machine that produces continuous, real-time x-ray images, allowing clinicians to observe internal structures as they move.

Fluoroscopy is an imaging procedure that produces continuous, real-time x-ray pictures, commonly used to watch swallowed contrast or guide device placement.

It stays in the body far longer than the rest of its class, which softens the effect of a missed dose and of stopping.

Fluphenazine is a first generation antipsychotic medication used mainly to manage schizophrenia and other conditions involving psychosis.

Alone among the SSRIs sold in the United States, it carries no approval for depression, its labeled uses being obsessive-compulsive and social anxiety disorder.

A radioactive substance being studied as an imaging agent in head and neck cancers and other types of cancer.

The removal of tissue or fluid with a thin needle for examination under a microscope.

A screening test looking for bleeding too slight to see, on the logic that bowel tumors leak before they cause symptoms.

Focal describes a finding, change, or process confined to one specific location rather than spread throughout an organ or tissue.

Folate is a B vitamin essential for making red blood cells and DNA, distinct from folic acid, its synthetic supplement form.

A substance that blocks the activity of folic acid.

A three-drug infusion schedule for advanced bowel cancer, its name assembled from the folinic acid and irinotecan it contains.

FOLFOX is a chemotherapy regimen combining three drugs to treat colorectal cancer, with several dosing variants used in different clinical situations.

Folinic acid is a form of folate used to counteract the toxic effects of certain drugs that block folic acid activity in cells.

A follicle is a small, sac like cluster of cells, describing both egg containing structures in the ovary and hair bearing structures in the skin.

A rare type of non-Hodgkin lymphoma (cancer of the lymphatic system) with large cells that look cleaved (split) or non-cleaved under the microscope.

Slow growth cuts both ways: the disease is usually widespread when found, yet often watched rather than treated at once.

An indolent (slow-growing) type of B-cell non-Hodgkin lymphoma (cancer of the lymphatic system) in which there are both small and large cancer cells.

Cancer that forms in follicular cells in the thyroid.

The giveaway is the pattern: every bump sits on a hair, which separates it from skin infections that spread without regard to follicles.

A hormone made in the pituitary gland.

Follow-up refers to the ongoing monitoring of a person's health or a study participant's status after initial treatment or evaluation.

Fondaparinux is a synthetic anticoagulant used to prevent and treat blood clots by blocking a specific clotting factor.

Anagency in the U.S.

The foreskin is a fold of skin that covers and protects the glans, or head, of the penis.

A form that must be filed by an investigator running a clinical trial to study a new drug or agent.

Formaldehyde is a simple, reactive chemical compound used as a preservative and disinfectant that is also classified as a known human carcinogen.

A substance being studied in the treatment of some types of leukemia and lymphoma.

Food carrying nutrients it never contained naturally, added deliberately to reach a whole population through the shopping basket.

A drug used together with other drugs to prevent and control nausea and vomiting caused by cancer treatment.

A drug used to treat infections with herpesviruses in people whose immune systems are weakened by AIDS.

A drug used to treat infections with herpesviruses in people whose immune systems are weakened by AIDS.

A substance being studied in the treatment of cancer.

Dividing the total dose of radiation therapy into several smaller, equal doses delivered over a period of several days.

A break and a fracture are the same event, and the choice of word reflects vocabulary rather than how serious the injury is.

Fragrance is a pleasant scent, often from added compounds in personal care products, that can act as an irritant for sensitive individuals.

The amount of the protein prostate-specific antigen (PSA) in the blood that is not attached to other proteins.

A highly reactive chemical that often contains oxygen and is produced when molecules are split to give products that have unpaired electrons (a process called oxidation).

Freeze-dried describes a substance preserved by freezing it and then removing its moisture through vacuum drying.

The air space behind the eyebrows that nobody is born with, and the one whose shape is distinctive enough to identify a person.

One of a group of substances that are found in several types of fruit and in milk.

A pituitary hormone that tells the ovaries to ripen an egg and the testicles to keep making sperm.

A substance being studied in the treatment of some types of cancer.

An abbreviation for a chemotherapy combination used with other types of therapy to treat colorectal cancer.

A procedure to destroy tissue (such as a tumor) using an electric current.

A tumor that is found in endocrine tissue and makes hormones (chemicals that travel in the bloodstream and control the actions of other cells or organs).

The fundus is the rounded base of a hollow organ farthest from its opening, a landmark used to describe findings in organs from the stomach to the eye.

A type of skin lesion that is marked by ulcerations (breaks on the skin or surface of an organ) and necrosis (death of living tissue) and that usually has a bad smell.

Any substance used to kill fungi (plant-like organisms that do not make chlorophyll), such as yeast and molds.

Closer relatives of animals than of plants, and wrapped in a cell wall humans have no equivalent of, which is what antifungal drugs exploit.

A gene made by joining parts of two different genes.

A protein made from a fusion gene, which is created by joining parts of two different genes.

Worry that will not switch off is the core of it, and the body keeps score through tension, tiredness and broken sleep.

Because gadolinium can pose risks for people with significantly reduced kidney function, its use during imaging is weighed carefully in that group.

A substance that is being studied in the treatment of cancer.

It is a reservoir rather than a producer, which is why the body manages without it once it has been removed.

Because early gallbladder cancer rarely causes noticeable symptoms, it is often identified only after the disease has already reached an advanced stage.

A procedure to detect areas of the body where cells are dividing rapidly.

Solid material that forms in the gallbladder or common bile duct.

A change in the heat and electricity passed through the skin by nerves and sweat.

A type of radiation therapy that uses gamma radiation.