Definition:Modulo Addition/Definition 2

Definition
Let $m \in \Z$ be an integer.

Let $\Z_m$ be the set of integers modulo $m$:
 * $\Z_m = \set {0, 1, \ldots, m - 1}$

The operation of addition modulo $m$ is defined on $\Z_m$ as:
 * $\forall a, b \in \Z_m: a +_m b$ equals the remainder after $a + b$ has been divided by $m$

Also see

 * Equivalence of Definitions of Integer Modulo Addition