1. < mathematics > A subset of the product of two sets, R : A x B. If (a, b) is an element of R then we write a R b, meaning 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).
See equivalence relation , partial ordering , pre-order , total ordering .
2. A table in a relational database .
(1995-02-28)