• synonyms


  1. next after the seventeenth; being the ordinal number for 18.
  2. being one of 18 equal parts.
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  1. an eighteenth part, especially of one (1/18).
  2. the eighteenth member of a series.
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Origin of eighteenth

before 900; Middle English eightenthe, eightethe, Old English eahtatēotha. See eighteen + -th2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for eighteenth


  1. (usually prenominal)
    1. coming after the seventeenth in numbering or counting order, position, time, etc; being the ordinal number of eighteen: often written 18th
    2. (as noun)come on the eighteenth
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    1. one of 18 approximately equal parts of something
    2. (as modifier)an eighteenth part
  1. the fraction that is equal to one divided by 18 (1/18)
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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 eighteenth


mid-13c., egtetenþe, modified, by influence of eighteen, from Old English eahtateoða; from eight + teoða "tenth" (see -ty (1)).

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Online Etymology Dictionary, © 2010 Douglas Harper