▾ Set of symbols
▾ Alphabet
▾ Deduction system
▾ Theory
▾ Zermelo-Fraenkel set theory
▾ Set
▾ Transitive set
▾ Ordinal number
▾ Cardinal number
▾ Set cardinality
Singleton set
Formulation 0
A D11: Set $X$ is a singleton set if and only if \begin{equation} |X| = 1 \end{equation}
Also known as
Enton set
Child definitions
» D3835: Duoton set
» D4316: Set of singletons
Results
» R2833: Nonempty set is singleton iff all elements equal each other