# Definition talk:Set Union

$\bigcup _{x \in A} B _{x} = \{ y : \exists x \in A: y \in B _{x} \}$. You might notice that this generalizes the $x \in \N$. This notation also allows $\bigcup A$ to be written $\bigcup _{x \in A} x$ Andrew Salmon 22:14, 2 December 2011 (CST)