A reference between two different or the same entity. Based upon the values of the entities.

• A. Entity
• B. Relationship
• C. Association
• D. Link

Answer: (B)

In data modeling, a reference between two entities, whether they are different types or the same type (a self-relationship), is called a relationship. It expresses how instances of one entity are connected to instances of another, and it hinges on the values stored in their keys to establish those links. Relationships can be one-to-one, one-to-many, or many-to-many, depending on how many instances on one side relate to how many on the other. For example, a record linking a student to a class shows the relationship based on the student’s key and the class’s key.

The other terms are more general: an entity is the object being described, not the link itself, and while association or link can describe connections informally, relationship is the precise term used in formal modeling to describe how entities are tied together.