▾ Set of symbols
▾ Alphabet
▾ Deduction system
▾ Theory
▾ Zermelo-Fraenkel set theory
▾ Set
▾ Transitive set
▾ Ordinal number
▾ Cardinal number
▾ Set cardinality
▾ Singleton set
▾ Duoton set
Trioton set
Formulation 0
A D11: Set $X$ is a trioton set if and only if \begin{equation} |X| = 3 \end{equation}