• Entity types that do not have key attributes of their own are called weak entity.

• Entities belonging to weak entity type are identified by being related to specific strong entities.

• These strong entities are called identifying entities and relationship with weak entity is called weak relationship.

Weak Entity is represented as:

Weak relationship is represented as:

• A weak entity has a partial key which is the attribute that can uniquely identify weak entities that are related to another strong entity.

• For example consider dependent entity, it is a weak entity as it do not have sufficient attributes to from a primary key.

• It is connected with a strong entity employee.

• Here the Name attribute is a partial key.

• Using attributes Name, Age and relation it is not possible to uniquely identify depandant.

• Thus dependent is weak entity and emp is corresponding identifying strong entity.