Cardinality

Cardinality describes the quantitative rating of an association or relationship between elements in a system or model. It specifies how many participants — objects, instances, modules, or other elements — take part in that association, typically expressed as a range such as one-to-one, one-to-many, or many-to-many.

Cardinality is most commonly encountered in data modeling and object-oriented design, where it constrains how many instances of one type may be associated with instances of another. It is a structural property of the relationship itself, independent of the behavior of the participants it connects.