• synonyms


[ih-rey-dee-uh ns]
noun Physics.
  1. incident flux of radiant energy per unit area.
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Origin of irradiance

First recorded in 1660–70; ir-1 + radiance
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for irradiance

Historical Examples of irradiance

  • Their irradiance was greenish, like the walls; but I was certain that these corpuscles did not come from them.

    The Metal Monster

    A. Merritt

  • The irradiance, almost as strong as daylight, but radically different, softened all surrounding objects.

    Ben Blair

    Will Lillibridge

British Dictionary definitions for irradiance


  1. the radiant flux incident on unit area of a surface. It is measured in watts per square metreSymbol: E e Also called: irradiation Compare illuminance
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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

Word Origin and History for irradiance


1660s, from irradiant (1520s), from Latin irradiantem (nominative irradians), present participle of irradiare (see irradiate). Related: Irradiancy (1640s).

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Online Etymology Dictionary, © 2010 Douglas Harper