## cardinality

(mathematics) The number of elements in a set. If two sets have the same number of elements (i.e. there is a bijection between them) then they have the same cardinality. A cardinality is thus an isomorphism class in the category of sets.

aleph 0 is defined as the cardinality of the first infinite ordinal, omega (the number of natural numbers).

Last updated: 1995-03-29

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