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

who, which, what, that, or their compounds beginning an adjective or noun clause: e.g., the ho use that Jack built; whatever you say.

a pronoun (as `that' or `which' or `who') that introduces a relative clause referring to some antecedent

words such as Which, that, whom, whose, where, when and so on. e.g. She describes the city where she grew up. The book that I am reading is about Online NetGrammar.

Relative pronouns are used to join two parts of a sentence together. For example, He’s the man who stole my car!, There’s a dog that lives down the road from me...

A pronoun that connects a dependent clause to a main clause in a sentence: who, whom, whose, which, that, what, whoever, whomever, whichever, and whatever.

(see Pronoun)

A relative pronoun is a pronoun that marks a relative clause within a larger sentence.