An Entity is a rectangular symbol representing an item in the system being modeled. An entity on a logical diagram will eventually become part of one or more tables in the physical database. Super- and sub-entities are supported. A sub-entity represents "a part of" or "a kind of" the super, or parent, entity. Membership in more than one sub-entity is not logically possible.

An entity is automatically transformed into a weak or associative entity based on the relationship with another entity.