What are the allowable values for an attribute in a database called?

The correct answer, "Domain," refers to the set of allowable values that an attribute in a database can hold. Each attribute in a database schema has specific constraints or rules that define what values are valid for that attribute. For example, if an attribute is defined as a date, its domain might consist of valid date formats or specific ranges of dates.

Understanding the concept of domain is crucial in database design, as it helps ensure data integrity by restricting input to acceptable values. By defining domains, database designers can implement validation checks, which prevent erroneous data entry that doesn't meet the specified criteria.

In contrast, other options such as "Entity," "Determinant," and "Attribute set" have distinct meanings in database terminology. An entity refers to an object or concept about which data is stored, a determinant is a concept related to functional dependencies in databases, and an attribute set implies a collection of attributes rather than the specific constraints on a single attribute.