Cardinality

Natural & Formal Sciences Dictionary
Cardinality is a measure of the number of elements in a set: finite sets have a natural finite cardinal, infinite sets are compared by the existence of bijections (same cardinality) or injections/surjections (≤ relation).

Cardinality

- Natural & Formal Sciences -
Mathematics & Logic Dictionary
The cardinality of a set is the equivalence class of sets equipotent (in bijection) to it; cardinality measures size up to bijection and distinguishes finite sizes and infinite sizes indexed by cardinals such as ℵ_0 or 2^{ℵ_0}.