# cardinality

## EnglishEdit

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### NounEdit

cardinality (plural cardinalities)

1. (set theory) Of a set, the number of elements it contains.
The empty set has a cardinality of zero.
• 2005 April 23, Johan de Jong, “Set Theory”, in The Stacks Project[1], retrieved 2018-2-26:
The cardinality of a set A is the least ordinal α such that there exists a bijection between A and α. We sometimes use the notation ${\displaystyle \alpha =|A|}$  to indicate this.
1. (data modeling, databases) The property of a relationship between a database table and another one, specifying whether it is one-to-one, one-to-many, many-to-one, or many-to-many.
2. (religion) The status of a cardinal