Definition:Equivalence Relation

Definition
A relation on a set $S$ which is:


 * reflexive,
 * symmetric and
 * transitive

is called an equivalence relation, or an equivalence, on $S$.

When discussing equivalence relations, various notations are used for $\left({x, y}\right) \in \mathcal R$. Examples are: and so on.
 * $x \equiv y \left({\mathcal R}\right)$
 * $x \sim y$

Specialised equivalence relations generally have their own symbols, which can be defined as they are needed.

Also see

 * Equivalence Class
 * Quotient Set
 * Quotient Mapping, also known as the Canonical Surjection


 * Relation Partitions a Set iff Equivalence