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 assure 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.
Null set was once a common synonym for "empty set", but is now a technical term in measure theory.
Read more about Empty Set: Notation, Properties
Famous quotes containing the words empty and/or set:
“I have heard of a minister, who had been a fisherman, being settled in Bridgewater for as long a time as he could tell a cod from a haddock. Generous as it seems, this condition would empty most country pulpits forthwith, for it is long since the fishers of men were fishermen.”
—Henry David Thoreau (1817–1862)
“One does not set fire to a world which is already lost.”
—Friedrich Dürrenmatt (1921–1990)