# Definition:Unit of Ring/Definition 2

Not to be confused with Definition:Unity of Ring.

## Definition

Let $\struct {R, +, \circ}$ be a ring with unity whose unity is $1_R$.

An element $x \in R$ is a unit of $\struct {R, +, \circ}$ if and only if $x$ is divisor of $1_R$.

## Also known as

Some sources use the term invertible element for unit of ring.