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:
“Come hither, all ye empty things,
Ye bubbles rais’d by breath of Kings;
Who float upon the tide of state,
Come hither, and behold your fate.
Let pride be taught by this rebuke,
How very mean a thing’s a Duke;
From all his ill-got honours flung,
Turn’d to that dirt from whence he sprung.”
—Jonathan Swift (1667–1745)
“Please do not take counsel of women who are so prejudiced that, as I once heard said, they would not allow a male grasshopper to chirp on their lawn; but out of your own great heart, refuse to set an example to such folly.”
—Frances E. Willard (1839–1898)