\begin{definition}[Definition:Order of Structure/Infinite Structure]
Let $\struct {S, \circ}$ be an algebraic structure.
Let the underlying set $S$ of $\struct {S, \circ}$ be infinite.
Then $\struct {S, \circ}$ is an '''infinite structure'''.
That is, $\struct {S, \circ}$ is an '''infinite structure''' {{iff}} $\struct {S, \circ}$ is not a finite structure.
\end{definition}