How is the number of attributes in a relation defined?

The term that correctly defines the number of attributes in a relation is referred to as the "relational degree." The relational degree, also known as the arity of a relation, quantifies how many attributes are present within that relation.

Each attribute corresponds to a column in a table, and the relational degree provides insight into the structure of the relation, indicating how much data can be stored or how complex the relation is. A higher degree means that the relation has more attributes, which can allow for more detailed data representation.

In contrast, cardinality pertains to the number of tuples (or rows) in a relation, which is a different aspect entirely. Data type relates to the kind of data an attribute can hold (such as integer, string, or date), and therefore is also not relevant to defining the number of attributes.

Understanding these distinctions is crucial when designing or querying a database, as they lay the foundation for effective data management and organization.