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.
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.
See Factorial number page.
the product of all the integers up to and including a given integer; "1, 2, 6, 24, and 120 are factorials"