\begin{definition}[Definition:Pairwise Disjoint/Family]
An indexed family of sets $\family {S_i}_{i \mathop \in I}$ is said to be '''pairwise disjoint''' {{iff}}:
:$\forall i, j \in I: i \ne j \implies S_i \cap S_j = \O$
Hence the indexed sets $S_i$ themselves, where $i \in I$, are referred to as being '''pairwise disjoint'''.
\end{definition}