a noun or pronoun which follows a linking verb and which is the same as the subject Quintus is a farmer.
a noun (or noun phrase ) that is used to predicate a description or identification of the subject
a noun that affirms as a quality, attribute, or property of a person or thing
a special noun in the predicate That means the same thing as the subject word
A noun used as a subject complement: Bromides are sedatives. See linking verb.