Definition:Disjoint Sets/Family

Definition
Let $I$ be an indexing set.

Let $\family {S_i}_{i \mathop \in I}$ be a family of sets indexed by $I$.

Then $\family {S_i}_{i \mathop \in I}$ is disjoint their intersection is empty:
 * $\displaystyle \bigcap_{i \mathop \in I} S_i = \O$

Also see

 * Definition:Pairwise Disjoint Family