What is a predicate adjective?
A predicate adjective describes the subject of the sentence and follows a linking (intransitive) verb.
Examples
1. Alice Hamilton was intelligent.
The word "intelligent" describes Alice Hamilton and follows the linking verb "was," so it is a predicate adjective.
2. She was tenacious.
Subject: She
Verb: was (a linking verb)
Predicate adjective: tenacious (describes the subject).
Predicate adjectives vs. predicate nominatives
A predicate nominative renames the sentence's subject; i.e. it offers another noun that denotes the subject.
Predicate nominatives, not like predicate adjectives, can be replaced by subjective pronouns.