1. 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 isn 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. In the theory of combinators, a combination denotes an expression in which function application is the only operation.(1995-04-10)