CARDINALITY is the term used in DATABASE relations to denote the OCCURRENCES of data on either SIDE of the relation.
There are 3 basic types of cardinality:
High data cardinality:
Values of a data column are very uncommon.
e.g.: email ids and the user names

Normal data cardinality:
Values of a data column are somewhat uncommon but never unique.
e.g.: A data column containing LAST_NAME (there may be several entries of the same last name)

LOW data cardinality:
Values of a data column are very usual.
e.g.: flag statuses: 0/1

Cardinality is the term used in database relations to denote the occurrences of data on either side of the relation.
There are 3 basic types of cardinality:
High data cardinality:
Values of a data column are very uncommon.
e.g.: email ids and the user names

Normal data cardinality:
Values of a data column are somewhat uncommon but never unique.
e.g.: A data column containing LAST_NAME (there may be several entries of the same last name)

Low data cardinality:
Values of a data column are very usual.
e.g.: flag statuses: 0/1