/Relative Clauses
B2Relative Clauses

Relative Pronoun or Interrogative

1

What is it?

Some pronouns — "who", "which", and "what" — can function as either relative pronouns (introducing a relative clause that describes a noun) or interrogative pronouns (introducing a direct or indirect question). The form is sometimes identical, so you need to analyse the sentence structure to identify which function the pronoun is performing. "That" is always relative, never interrogative. "What" is always interrogative (or exclamative), never a relative pronoun.

2

How to form it

SubjectPositiveNegativeQuestion
"Who" — relative pronounThe woman who called is my manager. (describes "the woman")
"Who" — interrogative pronounWho called? (direct question)I don't know who called. (indirect question)
"Which" — relative pronounThe book which she gave me is wonderful.
"Which" — interrogative pronounWhich book do you prefer? (direct question)Tell me which book you prefer. (indirect question)
"What" — interrogative onlyWhat did he say? / I know what he said."What" cannot be a relative pronoun.
"That" — relative onlyThe car that I drive is old."That" cannot be an interrogative pronoun.
  • • Relative pronouns introduce relative clauses that modify a noun already mentioned in the sentence.
  • • Interrogative pronouns ask or introduce indirect questions — there is no preceding noun they describe.
  • • "Who" relative: "the man who phoned" — "who" describes "the man".
  • • "Who" interrogative: "who phoned?" or "I know who phoned" — asking or reporting about an unknown person.
  • • "Which" relative: "the film which I preferred" — "which" describes "the film".
  • • "Which" interrogative: "which film did you prefer?" or "Tell me which film you prefer" — choosing between options.
  • • "What" is always interrogative or exclamative, NEVER a relative pronoun: NOT "the thing what I need".
  • • "That" is only a relative pronoun, NEVER interrogative.
3

When to use it

  1. 1

    Relative pronoun: describes a noun in the main clause

    The teacher who taught me Spanish retired last year.

  2. 2

    Interrogative (direct question)

    Who taught you Spanish?

  3. 3

    Interrogative (indirect question)

    I don't know who taught her Spanish.

  4. 4

    "What" is interrogative/exclamative only

    What a great film! / I know what you mean.

  5. 5

    "That" is relative only

    It's the only thing that matters.

4

Common mistakes

The thing what I need most is rest.

The thing that I need most is rest. / What I need most is rest.

"What" cannot be used as a relative pronoun. Use "that/which" to modify a noun, or rephrase with "what" as the subject.

I showed him the report what I had written.

I showed him the report that/which I had written.

"What" is not a relative pronoun. Use "that" or "which" to describe a specific noun.

Tell me the reason that you left.

Tell me why you left. / Tell me the reason why/that you left.

The indirect question "tell me why" uses "why" as an interrogative. "The reason that/why" is also fine.

5

Quick reference

  • Relative pronoun: describes/identifies a noun already in the sentence.
  • Interrogative pronoun: asks about an unknown person/thing, or introduces an indirect question.
  • "That" is relative ONLY. Never interrogative.
  • "What" is interrogative/exclamative ONLY. Never a relative pronoun.
  • "Who" and "which" can be either — analyse the sentence structure to tell them apart.
  • Key test: Is there a noun before the pronoun that it describes? If yes → relative. If no → interrogative.
6

Natural conversation example

Two detectives compare notes on a case.

P

Pax

Who found the document first?
C

Cleo

A security officer — the one who was on the night shift.
P

Pax

Do we know what was in the document?
C

Cleo

Yes. It listed names, which suggests this goes higher up.
P

Pax

Which names? The ones that appeared in the earlier report?
C

Cleo

Exactly. That's what makes this case so unusual.
P

Pax

Do you know who signed off on the original investigation?
C

Cleo

Not yet. But whoever it was clearly had access to classified files.

Practice Exercises

Write "relative" or "interrogative" to describe the function of the underlined word.

  1. 1.
    The student [who] won the prize has just graduated.
  2. 2.
    [Who] won the prize?
  3. 3.
    I don't know [which] route to take.
  4. 4.
    The route [which] she suggested took two hours longer.
  5. 5.
    Tell me [what] happened.
  6. 6.
    This is the film [that] everyone is talking about.
  7. 7.
    I asked [who] had written the report.
  8. 8.
    The person [who] wrote the report has since retired.
  9. 9.
    Do you know [which] team won?
  10. 10.
    She is the manager [that] authorised the transfer.
Whose or WhomAll Topics

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