- AKA: Ø, Λ, Null Set.
- See: Set System.
- (Wikipedia, 2015) ⇒ http://en.wikipedia.org/wiki/empty_set Retrieved:2015-6-1.
- In mathematics, and more specifically set theory, the empty set is the unique set having no elements; its size or cardinality (count of elements in a set) is zero. Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set; in other theories, its existence can be deduced. Many possible properties of sets are trivially true for the empty set.