Description: Axiom of Union. An axiom
of Zermelo-Fraenkel set theory. It states
that a set exists that includes the
union of a given set
i.e. the collection of all members of the members of . The
variant axun26344 states that the union itself exists. A
version with the
standard abbreviation for union is uniex26345. A version using class
notation is uniex6346.
The union of a class df-uni4067 should not be confused with the union of
two classes df-un3310. Their relationship is shown in unipr4079.
(Contributed by NM, 23-Dec-1993.)