Disjoint Sets

Definition

Let $A,B$: Two sets

If $A\cap B=\varnothing$

Then we say $A$ and $B$ are disjoint

Let $({\mathbf{A}}_n):=(A_1,A_2,\dots ,A_n)$ : Sequence of sets

If $A_i\cap A_j=\varnothing ,\forall i,j\in \mathbb{N},i\ne j$

Then we say ${\mathbf{A}}_n$ is mutually disjoint