You categorize an entity by looking at what kinds of descriptors contribute to its identifier. Following are the kinds of entity.
Independent. There are three variations of the independent entity shape:
Common independent entity. The identifier includes no links. The entity includes at least one attribute that contributes to the identifier and at least one attribute that does not.
Lonely-attribute independent entity. The identifier includes no links. The entity includes only one attribute, and that attribute constitutes the entity’s identifier.
Aggregate independent entity (sometimes simply called aggregate entity). The identifier includes no link. The entity includes two or more attributes, and ...