Fac*to"ri*al (?), a. 1. Of or pertaining to a factory. Buchanan.

2. (Math.) Related to factorials.

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 numbers from unity up to any given number.

• (mathematics) The result of multiplying a given number of consecutive integers from 1 to the given number. In equations, it is symbolized by an exclamation mark (!). For example, 5! = 1 * 2 * 3 * 4 * 5 = 120.