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


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  • sinus

    A cavity in a bone or other tissue. Commonly used to describe the cavities in the skull that open into…

  • sinew

    A tendon or fibrous cord.

  • sigmoid


  • sickle cell trait

    Inheriting the gene for sickle cell anemia from only one parent. It causes no symptoms.

  • sickle cell anemia

    A genetic condition characterized by abnormal red blood cells containing a defective form of hemoglobin. Sickle cell anemia occurs in…

  • Siamese twins

    Identical twins born joined together.

  • shunt

    To surgically divert the flow (such as of blood) from one organ or pathway to another.

  • shoulder

    The ball-and-socket joint connecting the arm with the body.

  • shock

    A disorder resulting from disruption of the circulation of the blood that can upset all body functions.

  • shingles

    A viral infection of certain sensory nerves that causes pain and blisters on the skin along the course of the…

  • shigellosis

    A diarrheal disease caused by Shigella bacteria.

  • serum

    The clear, yellowish-colored liquid portion of blood.

  • serotonin

    A chemical used to transmit information from one nerve cell to another.

  • serology

    The study of the antigen-antibody reaction.

  • septum

    A wall dividing an organ or cavity, as in the nose.

  • sepsis

    When disease-causing bacteria from an area of infection spread into the bloodstream and tissues.

  • sensorium

    The state of a person’s mental awareness.

  • seminiferous

    Carrying or producing semen.

  • semicircular canals

    The three loop-shaped tubular passages of the inner ear that control the sense of balance.

  • semen

    The ejaculate of the male consisting of sperm and secretions from the prostate, seminal glands and other glands.

  • seizure

    An attack of epilepsy.