In entity–relationship terminology, is a “relationship” an association between entity types (not between attributes), representing how entity instances are related?

Introduction / Context:
ER modeling distinguishes entities, attributes, and relationships. A frequent confusion is to think that relationships connect attributes. In fact, attributes describe entities (or relationships in some models), whereas relationships connect entity types and, by extension, their instances.

Given Data / Assumptions:

• An entity type models a set of similar real-world things (e.g., Customer, Order).
• An attribute is a property of an entity (e.g., Customer.email).
• A relationship connects entity types (e.g., Customer places Order).

Concept / Approach:
Proper definitions: relationship = association between entity types; attributes = descriptive properties, not nodes to be “related” themselves. Cardinality and participation define how many instances of one entity can or must be associated with instances of another entity via the relationship.

Step-by-Step Solution:

Verification / Alternative check:
Any standard ERD shows entity boxes (with attributes) connected by relationship lines; attributes are not directly linked to other attributes.

Why Other Options Are Wrong:

• Incorrect: would accept the wrong “attributes-to-attributes” notion.
• Binary-only: relationships can be unary, binary, ternary; definition remains.
• Normalization level does not affect the definition of a relationship.

Common Pitfalls:
Drawing relationships among attributes; mistaking foreign keys (attributes) for relationships themselves—FKs implement relationships but are not the conceptual relationship.

Final Answer:
Correct