## relation

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.

<*database*>

2. A table in a relational database.

Last updated: 1995-02-28

### Nearby terms:

reinvent the wheel ♦ **relation** ♦ relational algebra ♦ relational calculus

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