\begin{definition}[Definition:Group of Units/Ring]
Let $\struct {R, +, \circ}$ be a ring with unity.
Then the set $U_R$ of units of $\struct {R, +, \circ}$ is called the '''group of units''' of $\struct {R, +, \circ}$.
This can be denoted explicitly as $\struct {U_R, \circ}$.
\end{definition}