Empty set
This is an old revision of this page, as edited by Economist (talk | contribs) at 02:52, February 23, 2009. It may differ significantly from current revision.
In set theory, the empty set is the unique set that contains no element and is a subset of every other set. Its existence is postulated by the Axiom of empty set in the axioms of ZermeloâFraenkel set theory. Though this seems counterintuitive, the empty set is a subset of the empty set, and the empty set is disjoint with itself.