combination

1. mathematics A set containing a certain number of

objects selected from another set.

The number of combinations of r objects chosen from a set of n

is

n C r = n! / ((n-r)! r!)

where "n C r" is normally with n and r as subscripts or as n

above r in parentheses.

See also permutation.

2. reduction In the theory of combinators, a combination

denotes an expression in which function application is the

only operation.

(1995-04-10)