\begin{definition}[Definition:Pairwise Disjoint Events]
Let $\family {A_i}_{i \mathop \in I}$ be an indexed family of events in a probability space.
Then $\family {A_i}$ is '''pairwise disjoint''' {{iff}}:
:$\forall i, j \in I, i \ne j: A_i \cap A_j = \O$
That is, a set of events is '''pairwise disjoint''' {{iff}} every pair of them is disjoint.
\end{definition}