factorial

from WordNet (r) 3.0 (2006)

factorial
    adj 1: of or relating to factorials
    n 1: the product of all the integers up to and including a given
         integer; "1, 2, 6, 24, and 120 are factorials"

from The Collaborative International Dictionary of English v.0.48

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

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

from The Collaborative International Dictionary of English v.0.48

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]

from The Free On-line Dictionary of Computing (8 July 2008)

factorial

   <mathematics> The mathematical {function} that takes a
   {natural number}, N, and returns the product of N and all
   smaller positive integers.  This is written

   	N! = N * (N-1) * (N-2) * ... * 1.

   The factorial of zero is one because it is an {empty
   product}.

   Factorial can be defined {recursively} as

   	0! = 1
   	N! = N * (N-1)!		, N > 0

   The {gamma function} is the equivalent for {real numbers}.

   (2005-01-07)