[ kwo-dril-yuh n ]
/ kwɒˈdrɪl yən /

noun, plural quad·ril·lions, (as after a numeral) quad·ril·lion.

a cardinal number represented in the U.S. by 1 followed by 15 zeros, and in Great Britain by 1 followed by 24 zeros.


amounting to one quadrillion in number.

Origin of quadrillion

1665–75; quadr- + -illion (as in million)

OTHER WORDS FROM quadrillion

quad·ril·lionth, noun, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Examples from the Web for quadrillionth

  • But as this gives something like one thousand quadrillionth part of the density of water, we refuse to accept or even think of it.

British Dictionary definitions for quadrillionth

/ (kwɒˈdrɪljən) /


(in Britain) the number represented as one followed by 24 zeros (10 24)US and Canadian word: septillion
(in the US and Canada) the number represented as one followed by 15 zeros (10 15)


  1. amounting to this numbera quadrillion atoms
  2. (as pronoun)a quadrillion

Derived forms of quadrillion

quadrillionth, adjective

Word Origin for quadrillion

C17: from French quadrillon, from quadri- + -illion, on the model of million
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