# Definition:Disjoint Union (Set Theory)/Disjoint Sets

## Definition

Let $A$ and $B$ be disjoint sets, that is:

$A \cap B = \O$

Then the disjoint union of $A$ and $B$ can be defined as:

$A \sqcup B := A \cup B$

where $A \cup B$ is the (usual) set union of $A$ and $B$.