next after the fourteenth; being the ordinal number for 15.
being one of 15 equal parts.


a fifteenth part, especially of one (1/15).
the fifteenth member of a series.
Music. the interval of two octaves.

Origin of fifteenth

before 900; Middle English fiftenthe (see fifteen, -th2); replacing Middle English fiftethe, Old English fīftēotha Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for fifteenth



  1. coming after the fourteenth in order, position, time, etc. Often written: 15th
  2. (as noun)the fifteenth of the month


  1. one of 15 equal or nearly equal parts of something
  2. (as modifier)a fifteenth part
the fraction equal to one divided by 15 (1/15)
  1. an interval of two octaves
  2. one of two notes constituting such an interval in relation to the other, esp the one higher in pitch
  3. an organ stop of diapason quality sounding a note two octaves higher than that normally produced by the key depressed; a two-foot stop
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 fifteenth

late 14c., from fifteen + -th (1). By 15c. displacing forms derived from Old English fifteoða. Cf. Old Frisian fiftuda, Dutch vijftiende, German fünfzehnte, Old Norse fimmtandi, Gothic fimftataihunda.

Online Etymology Dictionary, © 2010 Douglas Harper