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 axun24744 states that the union itself exists. A
version with the
standard abbreviation for union is uniex24745. A version using class
notation is uniex4746.
The union of a class df-uni4044 should not be confused with the union of
two classes df-un3314. Their relationship is shown in unipr4056.
(Contributed by NM, 23-Dec-1993.)