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factorial

[fak-tawr-ee-uh l, -tohr-]
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noun
  1. Mathematics. the product of a given positive integer multiplied by all lesser positive integers: The quantity four factorial (4!) = 4 ⋅ 3 ⋅ 2 ⋅ 1 = 24. Symbol: n!, where n is the given integer.
adjective
  1. Mathematics. of or relating to factors or factorials.
  2. of or relating to a factor or a factory.

Origin of factorial

First recorded in 1810–20; factor + -ial
Related formsfac·to·ri·al·ly, adverb
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for factorially

factorial

noun
  1. the product of all the positive integers from one up to and including a given integer. Factorial zero is assigned the value of one: factorial four is 1 × 2 × 3 × 4 . Symbol: n !, where n is the given integer
adjective
  1. of or involving factorials or factors
Derived Formsfactorially, adverb
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 factorially

factorial

1816 (n.), 1837 (adj.), from factor + -al (2).

Online Etymology Dictionary, © 2010 Douglas Harper

factorially in Science

factorial

[făk-tôrē-əl]
  1. The product of all of the positive integers from 1 to a given positive integer. It is written as the given integer followed by an exclamation point. For example, the factorial of 4 (written 4!) is 1 X 2 X 3 X 4, or 24.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.