Definition:Cover of Set/Subset

Definition
Let $S$ be a set. Let $A \subseteq S$ be a subset.

Let $\mathcal C$ be a set of subsets of $S$.

Then $\mathcal C$ is a cover of $A$ $A \subseteq \displaystyle \bigcup \mathcal C$, where $\cup$ denotes union.

Also see

 * Definition:Open Cover of Subset