Definition:Pairwise Disjoint Events

Definition
Let $\left({A_i}\right)_i \mathop \in I$ and $B$ be an indexed set of events in a probability space.

Then $\left({A_i}\right)$ is pairwise disjoint iff:
 * $\forall i, j \in I, i \ne j: A_i \cap A_j = \varnothing$

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