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


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  • sacroiliac

    Having to do with the joint formed by the sacrum and the ilium in the lower back.

  • saccharin

    A compound that’s hundreds of times sweeter than table sugar. Used as an artificial sweetener.

  • sac

    Pouch; a bag-like structure.

  • rubeola

    A type of measles that can lead to serious complications and death.

  • rubella

    A mild childhood disease that causes fever and rash. Although rubella is mild in childhood, it’s dangerous to pregnant women…

  • roseola infantum

    A common viral infection of young children. Characterized by high fever, irritability and a faint rose-colored rash that appears on…

  • Rocky Mountain spotted fever

    An infectious disease spread by tick bites.

  • ringworm

    A fungal infection of the skin.

  • rickets

    A condition resulting from a vitamin D deficiency in childhood. Characterized by the softening of the bones and associated…

  • rhinorrhea

    Runny nose.

  • rhinoplasty

    Plastic surgery of the nose.

  • rhinitis

    Inflammation of the mucous membranes of the nose.

  • rheumatism

    Pain in the muscles and joints. Characterized by inflammation and stiffness. Sometimes used to describe arthritis, bursitis and sciatica.

  • retrovirus

    A virus that produces DNA from RNA (the opposite of the normal order). A group of viruses that includes…

  • retrobulbar

    Behind the eyeball.

  • retinopathy

    Degeneration of the retina.

  • retina

    The innermost layer of the eyeball. The retina contains the light-sensing rods and cones used for vision.

  • retardation

    Delay or halt of any process such as mental or physical development.

  • resuscitation

    Restoring the heartbeat and/or breathing in someone who’s apparently dead. Also called artificial respiration.

  • respiration

    The act or process of breathing. The process by which a living organism or cell takes in oxygen from the…

  • reservoir

    A medical term used to describe a source of organisms causing a disease.