A set having exactly one element . A singleton set is denoted by and is the simplest example of a nonempty set.
Singleton Set
See also
Empty Set, Nonempty Set, Singleton FunctionThis entry contributed by Margherita Barile
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Cite this as:
Barile, Margherita. "Singleton Set." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/SingletonSet.html