▾ Set of symbols
▾ Alphabet
▾ Deduction system
▾ Theory
▾ Zermelo-Fraenkel set theory
▾ Set
▾ Binary cartesian set product
▾ Binary relation
▾ Map
Multiset
Formulation 0
An D548: Ordered pair $M = (X, f)$ is a multiset if and only if
(1) $X$ is a D11: Set
(2) \begin{equation} f : X \to \mathbb{N} \cup \{ \infty \} \end{equation}