• synonyms


or ae·on

[ee-uh n, ee-on]
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  1. an indefinitely long period of time; age.
  2. the largest division of geologic time, comprising two or more eras.
  3. Astronomy. one billion years.
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Origin of eon

see origin at aeon
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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ages, aeon

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British Dictionary definitions for eon


  1. the usual US spelling of aeon
  2. geology the longest division of geological time, comprising two or more eras
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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 eon


1640s, from Latin aeon, from Greek aion "age, vital force, a period of existence, lifetime, generation;" in plural, "eternity," from PIE root *aiw- "vital force, life, long life, eternity" (cf. Sanskrit ayu "life," Avestan ayu "age," Latin aevum "space of time, eternity," Gothic aiws "age, eternity," Old Norse ævi "lifetime," German ewig "everlasting," Old English a "ever, always").

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Online Etymology Dictionary, © 2010 Douglas Harper

eon in Science


  1. The longest division of geologic time, containing two or more eras.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.