Axiom of union
= Axiom of union
{c}
{wiki=Axiom_of_union}
For every set $x$, there is a set $u=\bigcup x$ whose elements are exactly the elements of members of $x$:
$$
y\in u\quad\Longleftrightarrow\quad\exists z\in x\ (y\in z).
$$
= Axiom of union
{c}
{wiki=Axiom_of_union}
For every set $x$, there is a set $u=\bigcup x$ whose elements are exactly the elements of members of $x$:
$$
y\in u\quad\Longleftrightarrow\quad\exists z\in x\ (y\in z).
$$