出典:Wiktionary
cardinality (複数形 cardinalities)
(set theory): The cardinality of an infinite set is an infinite cardinal number. The smallest such number, called aleph-null and denoted ℵ₀, describes the natural numbers; the next is aleph-one. The cardinality of the real numbers is greater than aleph-null, though whether it is equal to aleph-one is the subject of the continuum hypothesis.
出典:Wikipedia
出典:『Wikipedia』 (2011/06/14 11:28 UTC 版)
In mathematics, the cardinality of a set is a measure of the "number of elements of the set". For example, the set A = {2, 4, 6} contains 3 elements, and therefore A has a cardinality of 3. There are two approaches to cardinality – one which compares sets directly using bijections and injections, and another which uses cardinal numbers.