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. Last updated: 1995-04-10