\begin{definition}[Definition:Open Cover]
Let $T = \struct {S, \tau}$ be a topological space.
Let $\CC$ be a cover for $S$.
Then $\CC$ is an '''open cover (of $T$)''' {{iff}}:
:$\CC \subseteq \tau$
That is, {{iff}} all the elements of $\CC$ are open sets.
\end{definition}