Which symbol is used in an entity-relationship (ER) diagram for an entity?

In an entity-relationship (ER) diagram, entities are represented using a specific geometric shape, which is the square (or rectangle). This symbol signifies a distinct object or concept, such as a person, place, thing, or event, that can have data stored about it. The purpose of the ER diagram is to visually depict the relationships and structures of data in a database, and by clearly designating entities with squares, it allows for easy recognition and differentiation from other components like attributes and relationships.

Attributes, which describe the properties of entities, are usually represented by ovals or circles, while relationships between entities often use diamonds. Lines connect these shapes to illustrate the connections and associations between entities and their attributes or the relationships to other entities. Understanding these standard symbols is crucial for accurately interpreting and creating ER diagrams, which are foundational in the design of relational databases.