Wh- pronoun

A wh- pronoun is a wh- word that’s a pronoun.

There are four main pronouns used in English; what, which, who and whose. A fifth, whom is also used in formal registers.

Form

Wh- pronoun	Case	Meaning
what	Common case	Refers to things (unlimited scope)
which	Common case	Refers to things (limited scope)
who	Common case/Subjective case	Refers to people, companies, organisations, etc.
whom	Accusative case
whose	Genitive case	Refers to possessors

Usage

Grammatically, they can be used:

1. As relatives, to introduce relative clauses, e.g. I know which one you want.
2. As interrogatives, in wh- clauses (wh- questions and wh- statements).

Syntactically, they can be used:

1. As independent pronouns; i.e. as subjects and objects.
2. All except what can be used as dependent pronouns (a type of determiner), e.g. which one would you like?. In traditional grammar, these are sometimes called "interrogative adjective", but are not adjectives.