next after the seventeenth; being the ordinal number for 18.
being one of 18 equal parts.


an eighteenth part, especially of one (1/18).
the eighteenth member of a series.

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. 2019

Examples from the Web for eighteenth

Contemporary Examples of eighteenth

  • I can't rebuild my apartment on the fifth floor while you keep your apartment on the eighteenth floor just as it is.

    The Daily Beast logo
    Hell, No, Not So Low

    Megan McArdle

    October 16, 2012

  • William Blake, the eighteenth century poet, illustrator, engraver and mystic, worked from home but lived in his imagination.

    The Daily Beast logo
    William Blake's Heavenly Imagination

    Chloe Malle

    November 12, 2009

Historical Examples of eighteenth

British Dictionary definitions for eighteenth



(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


  1. one of 18 approximately equal parts of something
  2. (as modifier)an eighteenth part
the fraction that is equal to one divided by 18 (1/18)
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)).

Online Etymology Dictionary, © 2010 Douglas Harper