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
