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[ih-rey-dee-ey-shuh n] /ɪˌreɪ diˈeɪ ʃən/
the act of irradiating.
the state of being irradiated.
intellectual or spiritual enlightenment.
a ray of light; beam.
Optics. the apparent enlargement of an object when seen against a dark background.
the use of x-rays or other forms of radiation for the treatment of disease, the making of x-ray photographs, the manufacture of vitamin D, etc.
exposure or the process of exposure to x-rays or other radiation.
Physics. irradiance.
Origin of irradiation
First recorded in 1580-90, irradiation is from the Late Latin word irradiātiōn- (stem of irradiātiō). See ir-1, radiation
Related forms
postirradiation, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for irradiation
Contemporary Examples
Historical Examples
  • The latter has a half-life of only 8.8 minutes and so counting must begin soon after the irradiation.

    The Atomic Fingerprint Bernard Keisch
  • The force of the irradiation has been directly proportional with the squares of the distances.

    Eureka: Edgar A. Poe
  • irradiation, by which alone these two truths are reconciled, is a consequent truthI perceive it.

    Eureka: Edgar A. Poe
  • However, is it not interesting to attribute the apparent movement to irradiation?

    Visual Illusions Matthew Luckiesh
  • Upon these are superposed the numerous psycho-physiological phenomena of color, irradiation, etc.

    Visual Illusions Matthew Luckiesh
  • It is classed as an effect of irradiation, and is caused by the sun shining through the depressions between the lunar mountains.

  • The phenomena of magnetism were ascribed by him to the irradiation of angels.

  • The shadows on the snow-fields deepened to purple below an irradiation of rose and pink and dazzling silver.

  • irradiation in general has been defined as the lateral diffusion of nervous stimuli beyond the actual stimulus.

    Visual Illusions Matthew Luckiesh
British Dictionary definitions for irradiation


the act or process of irradiating or the state of being irradiated
the apparent enlargement of a brightly lit object when it is viewed against a dark background
a shaft of light; beam or ray
  1. the therapeutic or diagnostic use of radiation, esp X-rays
  2. exposure of a patient to such radiation
another name for radiation, irradiance
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for irradiation

1580s, from French irradiation, from Latin *irradiationem, noun of action from past participle stem of irradiare (see irradiate). Originally of light (literally and figuratively); of X-rays, etc., from 1901.

Online Etymology Dictionary, © 2010 Douglas Harper
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irradiation in Medicine

irradiation ir·ra·di·a·tion (ĭ-rā'dē-ā'shən)

  1. Exposure or subjection to the action of radiation for diagnostic or therapeutic purposes.

  2. Medical treatment by exposure to radiation.

  3. The spread of a nervous impulse beyond the usual path of conduction.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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