Gain a better understanding of medical terminology by searching our dictionary of more than 1,300 terms.


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All terms that start with the letter H
  • histamine

    A substance released from certain cells in response to allergens, associated with the development of allergic symptoms, including itchy eyes,…

  • histoplasmosis

    A fungal disease caused by inhaling the spores of Histoplasma capsulatum.

  • HIV

    Human immunodeficiency virus. A virus that slowly destroys the immune system. The virus that causes AIDS.

  • hives

    A skin reaction characterized by swelling, itching and burning.

  • Hodgkin's disease

    A progressive form of lymphoma usually characterized by weakness, swollen lymph nodes, sweating, fever and weight loss.

  • homeopathy

    Medical treatment based on the theory that certain diseases can be cured by giving very small doses of substances that,…

  • homogenize

    To make more uniform in quality or consistency.

  • homosexual

    Having to do with the same sex.

  • hordeolum

    Inflammation of a gland on the eyelid. Also called a stye.

  • hormone

    A substance formed in an organ of the body and carried by body fluids to another organ or tissue, where…

  • host

    An organism that harbors and provides sustenance for another organism.

  • housemaid's knee

    Swelling just below the kneecap, caused by the buildup of fluid in response to the constant pressure of kneeling.

  • humerus

    The bone in the upper arm.

  • humidifier

    A device for adding moisture to the air.

  • Huntington's chorea

    A hereditary form of chorea (sudden, jerky motions of the arms or other parts of the body) that usually affects…

  • hydatid

    A cyst containing watery fluid and the larvae of certain tapeworms.

  • hydatid disease

    Infection with the larvae (cysts) of certain tapeworms.

  • hydatidiform mole

    A cystic tumor of the placental tissues of an abnormal pregnancy. Complications of this disorder include bleeding and infection.

  • hydrocele

    A painless swelling of the scrotum caused by the buildup of fluid in the outer covering of the testes.

  • hydrocephalus

    An enlargement of the head caused by the buildup of fluid within the ventricles of the brain. Also called “water…

  • hygiene

    The science of health and its maintenance.