Definition:Pairwise Disjoint Events

Definition
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 :
 * $\forall i, j \in I, i \ne j: A_i \cap A_j = \O$

That is, a set of events is pairwise disjoint every pair of them is disjoint.