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 R
  • rabies

    A fatal, if untreated, viral disease of mammals that’s spread to humans by the bite of infected animal.

  • rad

    Radiation absorbed dose. A unit of measurement of the absorbed dose of ionizing radiation.

  • radiculopathy

    A disease or other problem affecting a nerve root.

  • radioisotope

    A radioactive form of an element. Used in certain diagnostic tests.

  • radiology

    The branch of medicine that deals with the use of x-rays.

  • radon

    A colorless, radioactive gas produced by the decay of radium. The presence of sufficient quantities of this gas in homes…

  • rash

    Visual marks or spots that appear on the skin.

  • Raynaud's phenomenon

    A circulation disorder characterized by changes of blood flow, resulting in the hands and feet becoming pale, followed by redness…

  • recrudescence

    To reoccur after a temporary absence.

  • rectum

    The last portion of the large intestine.

  • reflux

    A return flow.

  • refraction

    1. The bending of a ray or wave of light from one medium to a medium of a different density…

  • regurgitation

    The return of partly digested food from the stomach to the mouth or of blood in a reverse direction through…

  • rehabilitation

    The process of restoring one’s ability to live as normally as possible after an injury or illness.

  • Reiter's syndrome

    A complex group of symptoms marked by inflammation of the urethra or cervix, conjunctiva and joints.

  • relapse

    The return of a disease after its apparent resolution.

  • REM

    Rapid eye movement. The phase of sleep associated with dreaming and distinguished from the other stages of sleep by rapid…

  • remedy

    Anything that cures.

  • remission

    Improvement of the symptoms of a disease.

  • renal

    Having to do with the kidney.

  • reservoir

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