Question: An entity set may not have sufficient attributes to form a primary key; such an entity set is termed as______

Answer:

For example consider the entity set payment, which has the three attributes; payment –number, payment-date, and payment-amount. Payment-numbers are typically sequence numbers, starting from 1.generated separately for each loan. Thus although each payment entity is distinct, payment for different loan may share the same payment numbers. Thus this entity set does not have a primary key; it is weak entity set.