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.
Famous quotes containing the words empty and/or set:
“Poetry isnt a profession, its a way of life. Its an empty basket; you put your life into it and make something out of that.”
—Mary Oliver (b. 1935)
“Narcissus does not fall in love with his reflection because it is beautiful, but because it is his. If it were his beauty that enthralled him, he would be set free in a few years by its fading.”
—W.H. (Wystan Hugh)