[kwo-dril-yuh n]

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)
Related formsquad·ril·lionth, noun, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for quadrillion

Historical Examples of quadrillion

  • At this rate of growth from a single cholera bacillus sixteen quadrillion might arise in a single day.

    Disease and Its Causes

    William Thomas Councilman

  • Quadrillion, kwod-ril′yun, n. a million raised to the fourth power, represented by a unit with twenty-four ciphers.

  • "Three quadrillion times, my son," replied his father with perfect accuracy and a spirit of hourly freshness.

    The Kentucky Warbler

    James Lane Allen

  • For the enormous majority of us there is no difference in this respect between a hundred and a quadrillion.

    Getting Married

    George Bernard Shaw

  • Their velocity was six hundred and sixty quadrillion miles per second!

    Invaders from the Infinite

    John Wood Campbell

British Dictionary definitions for quadrillion



(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 Formsquadrillionth, 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

Word Origin and History for quadrillion

1670s, from French quadrillion (16c.) from quadri- "four" (see quadri-) + (m)illion. Cf. billion. In Great Britain, the fourth power of a million (1 followed by 24 zeroes); in the U.S., the fifth power of a thousand (1 followed by 15 zeroes).

Online Etymology Dictionary, © 2010 Douglas Harper