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:
“There is the empty chapel, only the wind’s home.
It has no windows, and the door swings,
Dry bones can harm no one.”
—T.S. (Thomas Stearns)
“To divide one’s life by years is of course to tumble into a trap set by our own arithmetic. The calendar consents to carry on its dull wall-existence by the arbitrary timetables we have drawn up in consultation with those permanent commuters, Earth and Sun. But we, unlike trees, need grow no annual rings.”
—Clifton Fadiman (b. 1904)