\begin{definition}[Definition:Section of Étalé Space]
Let $T = \struct {S, \tau}$ be a topological space.
Let $\FF$ be a presheaf of sets on $T$.
Let $\struct {\map {\mathrm {\acute Et} } \FF, \pi}$ be its étalé space.
Let $U \subseteq S$ be open.
\end{definition}