\begin{definition}[Definition:Equivalence Relation/Also denoted as]
When discussing equivalence relations, various notations are used for $\tuple {x, y} \in \RR$.
Examples are:
:$x \mathrel \RR y$
:$x \equiv \map y \RR$
:$x \equiv y \pmod \RR$
and so on.
Specialised equivalence relations generally have their own symbols, which can be defined as they are needed.
Such symbols include:
:$\cong$, $\equiv$, $\sim$, $\simeq$, $\approx$
\end{definition}