The term complement comes from the verb to complete. The predicate nominative and predicate adjective complete the meaning of a state-of-being or linking verb. The most common linking verb is to be, with its forms am, is, are, was, were, being, been. Other verbs, like seem and appear, also function in this way.
The predicate nominative (abbreviated PN) completes the verb and renames the subject of the verb. The predicate adjective (abbreviated PA) completes the verb and describes the subject.
The predicate complement is also called the subject complement because it restates or describes the subject.
The predicate nominative is a noun or pronoun that completes the meaning of a linking verb.
Sometimes students confuse direct objects and predicate complements. One way to tell them apart is to reverse the sentence. If the sentence still makes sense after being reversed, the word that answers “What?” after the verb is a complement. Compare:
Baxter is an excellent typist.
An excellent typist is Baxter.
The reversed sentence still makes sense; “an excellent typist” is a complement.
Baxter typed the report.
The report typed Baxter.
The reversed sentence is nonsense; “the report” is a direct object.
When the predicate nominative is a pronoun, traditional grammar says it should be in the nominative (subject) case. That’s logical because the complement restates the subject. English idiom and logic, however, are not always on the best of terms. Consider:
Is Dr. Singh the man at the dais? Yes, that’s he.
Because he is a predicate nominative in this sentence, the subject form he is correct. However, most native speakers would probably say “Yes, that’s him.”
The predicate adjective follows a linking verb and describes its subject:
You seem sad. (predicate adjective)
In certain light, the fish appears transparent. (predicate adjective)
Other verbs commonly used to express a state of being are:
Note: some of these verbs can also be used as action verbs. If the verb conveys an action, the word that follows is a direct object (DO). If the word that follows the verb describes the subject, it’s a predicate adjective (PA):
I feel sad. (PA)
I feel the wall. (DO)
He made me mad. (PA)
I made cookies. (DO)
That smells bad. (PA)
Wake up and smell the roses. (DO)
Every day you grow older. (PA)
The farmer grows strawberries. (DO)
The angry dictator turned blue. (PA)
The ox turned the wheel. (DO)
That music sounds discordant. (PA)
The bugler sounded the alarm. (DO)