Predicate Nominative

Predicate Nominative: A second type of subject compliment- a noun, group of nouns, or noun clause that remanes the subject. It, like the predicate adjective, follows a linking verb and is located in the predicate of the sentence.

Example:
" Col. Grangerford was a gentleman, you see."
                                        (Huckleberry Finn, Pg.105)

In this sentence the predicate nominative is "gentleman" which is describing Col. Grangerford.