What is referred to as the primary key that is referenced by a foreign key?

The term that is used to describe a primary key which is referenced by a foreign key is known as the parent key. In relational database design, relationships between tables are established using keys. The primary key in one table uniquely identifies each record and is used to create a link to another table via a foreign key.

When a foreign key is defined in a child table, it refers to the primary key in the parent table. This establishes a parent-child relationship where the parent key is the primary key of the table being referenced. It is crucial in maintaining referential integrity within the database, ensuring that every foreign key entry corresponds to a valid primary key entry, thus enforcing a valid connection between the two tables.

Contextually, the other options either do not address the question correctly or pertain to different concepts within database design. An intermediate entity typically refers to a table that serves as an association or junction between two tables in a many-to-many relationship. Null indicates the absence of a value and does not apply to the concept of keys. Simply mentioning a primary key does not specify its relationship to a foreign key, which is why understanding the term "parent key" is essential for grasping these relationships.