1. A subset of the product of two sets,
R : A x BIf (a, b) is an element of R then we write
a R bmeaning a is related to b by R. A relation may be: reflexive (a R a), symmetric (a R b => b R a), transitive (a R b & b R c => a R c), antisymmetric (a R b & b R a => a = b) or total (a R b or b R a). Relations are most commonly between two sets (binary relations) but could be between more than two. See equivalence relation, partial ordering, pre-order, total ordering.
Last updated: 1995-02-28