Definition:Set of Residue Classes

Definition
Let $z \in \R$.

Let $\mathcal R_z$ be the congruence relation modulo $z$ on the set of all $a, b \in \R$:
 * $\mathcal R_z = \left\{{\left({a, b}\right) \in \R \times \R: \exists k \in \Z: a = b + k z}\right\}$

Let $\left[\!\left[{a}\right]\!\right]_z$ be the residue class of $a$ (modulo $z$).

The quotient set of congruence modulo $z$ denoted $\R_z$ is:
 * $\R_z = \dfrac \R {\mathcal R_z}$

Thus $\R_z$ is the set of all residue classes modulo $z$.

It follows from the Fundamental Theorem on Equivalence Relations that the quotient set $\R_z$ of congruence modulo $z$ forms a partition of $\R$.

Also see

 * Definition:Integers Modulo m