Definitions for "Relative pronoun"
A noun substitute (who, whom, whose, that, which, what, whoever, whomever, whichever, whatever) used to introduce subordinate clauses: He has an aunt who is a principal [adjective clause introduced by the relative pronoun who]. OR Whoever becomes treasure
(who, whom, which, that) introduce clauses that describe nouns or pronouns.
a pronoun which introduces a relative clause. The relative pronoun agrees with its antecedent in number and gender, while its case comes from its use in its own clause. The man whom we saw is tall. qui quae quod