Relative clause - Wikipedia
https://en.wikipedia.org/wiki/Relative_clauseA relative clause is typically a clause that modifies a noun or noun phrase, and uses some grammatical device to indicate that one of the arguments within the relative clause has the same referent as that noun or noun phrase. For example, in the sentence I met a man who wasn't there, the subordinate clause who wasn't there is a relative clause, since it modifies the noun man, and uses the pronoun who to indicate that the same "man" is referred to within the subordinate claus…