Definition of


  1. (noun, phenomenon) energy that is radiated or transmitted in the form of rays or waves or particles
  2. (noun, act) the act of spreading outward from a central source
  3. (noun, state) syndrome resulting from exposure to ionizing radiation (e.g., exposure to radioactive chemicals or to nuclear explosions); low doses cause diarrhea and nausea and vomiting and sometimes loss of hair; greater exposure can cause sterility and cataracts and some forms of cancer and other diseases; severe exposure can cause death within hours
  4. (noun, process) the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
  5. (noun, event) the spread of a group of organisms into new habitats
  6. (noun, body) a radial arrangement of nerve fibers connecting different parts of the brain
  7. (noun, act) (medicine) the treatment of disease (especially cancer) by exposure to a radioactive substance

via WordNet, Princeton University

Origin of the word Radiation

  1. 1555, from L. radiationem (nom. radiatio) "a shining, radiation," noun of action from radiare "to beam, shine," from radius "beam of light" (see radius). more

via Online Etymology Dictionary, ©2001 Douglas Harper

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