Subject complement - Wikipedia
https://en.wikipedia.org/wiki/Subject_complementIn grammar, a subject complement or predicative of the subject is a predicative expression that follows a linking verb (copula) and that complements the subject of the sentence by either (1) renaming it or (2) describing it. It completes the meaning of the subject. In the former case, a renaming noun phrase such as a noun or pronoun is called a predicative nominal. An adjective following the copula and describing the subject is called a predicative adjective. In either case th…