Weak Entity Types

An entity that does not have a key attribute. A weak entity must participate in an
identifying relationship type with an owner or identifying entity type.
Entities are identified by the combination of:
A partial key of the weak entity type
The particular entity they are related to in the identifying entity type.
A DEPENDENT entity is identified by the dependent’s first name, and the specific
EMPLOYEE with whom the dependent is related.
Name of DEPENDENT is the partial key.
DEPENDENT is a weak entity type.
EMPLOYEE is its identifying entity type via the identifying relationship type