Definition:Equivalence Relation/Also denoted as

Definition
When discussing equivalence relations, various notations are used for $\left({x, y}\right) \in \mathcal R$.

Examples are:
 * $x \equiv y \left({\mathcal R}\right)$
 * $x \equiv y \pmod {\mathcal R}$
 * $x \sim y$

and so on.

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