An interrogative pronoun is a word that asks a question and stands in for the unknown answer. English has five of them: who, whom, whose, which, and what.
Each one points at a different kind of missing information — a person, a possessor, a choice from a set, or an open-ended thing. Choosing the right one is mostly about matching the pronoun to what you don't yet know.
| PRONOUN | ASKS ABOUT | EXAMPLE |
|---|---|---|
| who | a person (subject) | Who called? |
| whom | a person (object, formal) | Whom did you invite? |
| whose | a possessor | Whose keys are these? |
| which | a choice from a known set | Which coat is yours? |
| what | an open-ended thing | What do you want? |
Who — the subject pronoun
Who asks about a person who performs the action. It stands where the subject of the verb would go in the answer.
A useful test: if the answer would be he, she, or they, then who is correct. Daniel called me → Who called me?
Whom — the object pronoun
Whom asks about a person who receives the action. It replaces the object of a verb or a preposition.
The test mirrors the one for who: if the answer would be him, her, or them, then whom is technically correct. I invited Maria → Whom did you invite?
In modern everyday English, most speakers use who in both positions — Who did you invite? sounds natural, and Whom did you invite? sounds noticeably formal. Whom survives mainly in formal writing and after a preposition, where to whom or for whom still feels right.
Whose — the possessive pronoun
Whose asks who something belongs to. The answer is always a possessor.
Do not confuse whose with who's. Whose asks about ownership; who's is a short form of who is or who has.
Which — choice from a known set
Which is used when the answer comes from a limited, identifiable group. The set may be stated in the question, visible in the situation, or clear from context.
The key signal is that both speakers already know the options. Which invites the listener to pick from them.
What — open-ended
What is used when the range of possible answers is wide or undefined. Nothing limits the choice in advance.
Which vs what — the clearest rule
The split between which and what is the single most useful distinction in this lesson.
- Which — closed set, options already known.
- What — open question, no fixed set.
In the first question, the speaker offers two options. In the second, any answer is possible — English, Japanese, Arabic, any number of them.
Pronoun or determiner?
The same five words can also appear right before a noun. In that position they are determiners, not pronouns.
The meaning is similar, but the grammar role differs: a pronoun replaces a noun, a determiner introduces one. This lesson covers the pronoun use. The determiner use is covered separately.
Compound forms: whoever, whatever, whichever
Adding -ever to who, whom, what, or which creates a compound interrogative pronoun. These forms add emphasis and usually signal surprise, confusion, or mild disbelief.
These are uncommon in everyday speech and belong mostly to formal or literary writing. A plain who, what, or which is almost always the natural choice.
Common mistakes
Who vs whom
Whose vs who's
Which vs what
Whose as ownership