Predicate nominative: a word in the predicate that renames the subject:
My friend is a doctor.
Dinner tonight will be spaghetti.
•	Sentences with predicate nominatives will have linking verbs.

Predicate adjective: an adjective in the predicate that is modifying or describing some word in the subject.
This is difficult.
Disneyland is fun.
•	Sentences with predicate adjectives will have linking verbs.