In an ER diagram, which element describes properties of an entity?

• A. Entity
• B. Attribute
• C. Relationship
• D. Constraint

Answer: (B)

An ER diagram uses attributes to capture the properties or characteristics of an entity. An entity represents the thing we store data about, such as a Customer or Product, while the attributes attached to that entity describe its details—like CustomerID, Name, Email, or Price. Attributes can be simple (a single value), composite (such as Address, broken into Street, City, State), or derived (computed from other attributes, like Age from BirthDate). The other elements describe relationships or rules: a relationship shows how entities are linked, and constraints specify rules such as cardinality or mandatory fields. So, the properties of an entity are described by its attributes, not by the entity itself, a relationship, or a constraint.