Dictionary of Medical Terms

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 A
  • ADH

    Antidiuretic hormone. One of the hormones produced by the pituitary gland. A shortage of this hormone causes increased loss of…

  • adhesion

    The sticking of one surface to another. This can occur when scar tissue causes organs or loops of intestine to…

  • adipose fatty cells

    Special cells in which fat is stored when a person’s caloric intake is greater than that required by one’s…

  • adrenal glands

    Located on top of the kidneys, these glands produce hormones helpful in regulating the body’s metabolism.

  • adrenaline

    Epinephrine. One of several hormones produced by the adrenal glands.

  • aerobic

    Requiring the use of oxygen. Exercise that conditions the heart and lungs by increasing the efficiency of oxygen intake by…

  • afterbirth

    The placenta, which is attached to the fetus by the umbilical cord and must be delivered after the baby.

  • AIDS

    Acquired immunodeficiency syndrome. A disease of the immune system caused by the HIV virus.

  • airway

    The passage by which air enters and exits the lungs.

  • albinism

    The absence of all normal body pigmentation at birth, a condition that can occur in all races.

  • albino

    A person with albinism.

  • albumin

    A water-soluble protein found in milk, egg, muscle, blood and many vegetable tissues and fluids.

  • aldosteronism

    A condition resulting when the adrenal glands produce too much of the hormone aldosterone, which regulates fluids and salt in…

  • alimentary

    Having to do with food or nutrition. The alimentary tract is the digestive tract.

  • allergen

    A substance capable of producing an allergic reaction.

  • allergy

    An exaggerated immune response to substances in the environment.

  • alopecia

    Hair loss, especially of the head.

  • alpha1-antitrypsin deficiency

    Congenital lack of an enzyme that leads to cirrhosis of the liver and obstructive lung disease.

  • altitude sickness

    A potentially fatal illness caused by being at altitudes high enough to reduce the amount of oxygen available to the…

  • alveoli

    The sacs in the lungs at the ends of the smallest airways where oxygen is exchanged for carbon dioxide in…

  • amblyopia

    Impaired vision without an apparent cause.