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:

“In the Lord’s Prayer, the first petition is for daily bread. No one can worship God or love his neighbor on an *empty* stomach.”

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—William Shakespeare (1564–1616)