\begin{definition}[Definition:Entourage]
Let $S$ be a set.
Let $\UU \subseteq \powerset {S \times S}$ be a quasiuniformity on $S$.
An element $u \in \UU$ of such a quasiuniformity is known as an '''entourage''' of $\UU$'''.
Note that an entourage of $\UU$ actually ''is'' a relation on $S$.
\end{definition}