Primary Key of weak entity DependentAn ER model or Entity Relationship model is a data representation model that is used to represent the business rules of any problem set.The business rules are the guidelines and narration scripts that guide the database models and help the designers to develop the system by fully abiding with the business policies, guidelines, protocols and procedures.By any means the information system that caters to the organization must cater to its needs and abide by its rules to develop an efficient database and system.Entities are physical world objects that form the basic locks around which the whole problem set revolves. For example, in a convenience store data model, the entities can be employee, inventory, payroll etc.Weak Entity A weak entity is dependent on another entity, that is$,$ it cannot exist in the data model if another entity is not present on which it is dependent.For example, an entity SPOUSE can only exist in the ER diagram if$,$ the entity EMPLOYEE has an instance in it$.$