What is the definition of cardinality in SQL

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My book definition of Database Systems does not match with that of the WIKIpedia, which one is correct and which one should I follow?

School Book: "The cardinality of a relation is the number of tuples it contains. By contrast, the number of tuples is called the cardinality of the relation and this changes as tuples are added or deleted. High-cardinality - many tuples, low-cardinality - few tuples."

Wikipedia: "Cardinality refers to the uniqueness of data values contained in a particular column (attribute) of a database table. The lower the cardinality, the more duplicated elements in a column. There are 3 types of cardinality: high-cardinality, normal-cardinality, and low-cardinality."
Feb 18 in Database by Neha
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