A subject complement is a word or group of words within the complete
predicate that either identifies (with a predicate nominative) or describes (with
a predicate adjective) the subject (doer of the action). There are two types of
subject complements—the predicate adjective (the describer) and the predicate
nominative (the identifier).
As an example, in the sentence, ‘‘Our Town is a play written by Thornton
Wilder,’’ the complete predicate, is a play written by Thornton Wilder, includes
play (predicate nominative), the word that identifies what Our Town is. In
the sentence, ‘‘The play was interesting and inspirational,’’ the complete
predicate, was interesting and inspirational, includes the words interesting and
inspirational (two predicate adjectives) to describe what the play was.
The subject complement is underlined in these sentences.
O’Hare is a very busy airport. (predicate nominative)
Mike Smith is a terrific friend. (predicate nominative)
Indiana’s capital city is Indianapolis. (predicate nominative)
She was the first president of that association. (predicate nominative)
Mitchell’s report was factually correct. (predicate adjective)
The lake’s water was crystal clear. (predicate adjective)
Gary’s parents and grandparents are quite successful in the business world.
The basement was moldy, dusty, and unpainted. (predicate adjectives)