Definition:Congruence (Number Theory)/Notation

Definition
The relation $x$ is congruent to $y$ modulo $z$, usually denoted:
 * $x \equiv y \pmod z$

is also frequently seen denoted as:
 * $x \equiv y \ \paren {\mathop {\operatorname{modulo} } z}$

Some (usually older) sources render it as:
 * $x \equiv y \ \paren {\mathop {\operatorname{mod.} } z}$