An entity is a distinct person, object, place, event, or concept that a system must represent.
Each entity has its own identity. Moreover, attributes describe its properties. For example, a Customer may have a customer number, name, and address.
Relationships connect entities to other elements. In addition, multiplicities define how many instances may participate in each relationship. Therefore, they help teams express structural rules clearly.
An entity model usually shows a stable information structure. However, teams may use separate models or attributes to describe history, states, and changes over time.
Generalization can combine shared properties of similar types. Meanwhile, constraints can define additional rules that the basic structure cannot express.
Clear entities, attributes, relationships, and constraints support consistent requirements, data models, and system designs.
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