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The Collaborative International Dictionary of English v.0.48 (gcide)

Factorial \Fac*to"ri*al\, a.
1. Of or pertaining to a factory. --Buchanan.
[1913 Webster]

2. (Math.) Related to factorials.
[1913 Webster]


Factorial \Fac*to"ri*al\, n. (Math.)
(a) pl. A name given to the factors of a continued product
when the former are derivable from one and the same
function F(x) by successively imparting a constant
increment or decrement h to the independent variable.
Thus the product F(x).F(x h).F(x 2h) . . . F[x
(n-1)h] is called a factorial term, and its several
factors take the name of factorials. --Brande & C.
(b) The product of the consecutive whole numbers from
unity up to any given number; thus, 5 factorial is the
product of 5 times four times three times two times
one, or 120.
[1913 Webster PJC]