In a question like "Who hears a noise?", is the subject of the sentence who?

I can think of a few tests for subjects like: "the subject is the phrase that inverts with the auxiliary to form a question". But this is a question and there is no auxiliary. We could say that's because it's a subject, but that would be just to presuppose that it's a subject in the first place.

I can think of tests like: "the form of the verb will agree with the number of the subject", but on the other hand who does not seem to have fixed grammatical number, and it sometimes seems like who might actually be agreeing with noun phrases later in the sentence:

  • Who are the most prolific writers of our age?
  • Who is the most prolific writer of our age?

There are also tests like "the subject is usually the first noun phrase in the sentence". But of course if we have a question like:

  • Who have you bitten?

... you, not who seems to be the subject. The first noun phrase test is not very good.

I also know that some theories of grammar say that there is a gap in wh- questions that the wh- word is extracted from. So can this gap for instance be the real object of a question? If so, is there a gap in questions like mine functioning as subject?[See community wiki post in the linked to question]

How can we show whether who is really the subject of my original example question? And how about other wh- words like what? Can they (also) function as subjects?

  • A quick look in a basic grammar or even Cambridge Dictionaries Online is all that is needed here. Commented Apr 2, 2015 at 23:27
  • Can you give me a link?
    – Droonkid
    Commented Apr 2, 2015 at 23:27
  • There's a link in his comment (Cambridge Dictionaries). Commented Apr 2, 2015 at 23:37
  • There wasn't before.
    – Droonkid
    Commented Apr 2, 2015 at 23:37
  • 1
    This is an interesting question which has been argued both ways in the linguistic literature. I was halfway through typing up an answer when I was notified that the question was closed, and so I had to discard what I had written. It's pretty irritating when people through ignorance decide that a question does not merit an answer.
    – Greg Lee
    Commented Apr 3, 2015 at 0:34

3 Answers 3


Both sides of this question have been argued in the linguistic literature. "who" could be a topic, and then the sentence structure would be

[who [ __ hears a noise]]

on the analogy of other wh-questions with a wh-word moved to the top of the structure and leaving a gap, __, where it once was. Or, perhaps questions whose subject is a wh-word simply don't need to be changed by moving the wh-word to the front, because, well, it's already there. In that case, we have

[who hears a noise]

and "who" is simply a subject.

There are a number of grammatical theories which do not permit stating grammatical relations in terms of word order, but only structural relationships, so such theories would presumably not recognize the logic of the argument that a wh-word subject must remain a subject in a question, because it is already at the front of the sentence, where it needs to be. (Such "order free" theories are Chomsky's latest theories (I think), dependency grammar, relational grammar, and GPSG.)

You might think that the subject-agreement in the verb "hears" with the singular "who" shows that "who" is a subject. And perhaps that is evidence, but a follower of the east coast school of linguistics would assume that the gap created by extracting the subject is a "trace" which is coindexed with the former subject, so the verb agreement can still be correctly described.

There is an argument for the second no-movement treatment quoted and discussed in the book Generalized Phrase Structure Grammar, and the argument itself (if I recall correctly, due to Pauline Jacobson) is based on so-called parasitic gaps. In the Wikipedia entry for Parasitic gap, this illustration is given:

Which explanation did you reject __1 without first really considering __2?

where the first gap must be higher up in the structure tree than the second (parasitic) gap. The relevance of parasitic gaps here is that they give us a diagnostic for detecting a gap in subject position. A subject gap, since it is highest in the structure of its clause, should license a parasitic gap elsewhere in the clause. But if there is no subject gap, there won't be any parasitic gap, because parasitic gaps depend for their existence on a gap higher up.

So, we can construct a test case from the above parasitic gap sentence by making it a passive whose subject is the wh-expression:

*Which explanation __1 was rejected by you without first really considering __2?

This is ungrammatical. If there were really a subject gap, it should have been okay. So, we can conclude that there is no subject gap and that a wh-subject in a question remains in place. I know of no evidence on the other side of this question, so that is my conclusion.

  • Worth waiting for. Odds on Droonkid having asked this when given a homework, and reproducing it for teacher? I hope other analyses are forthcoming. Commented Apr 7, 2015 at 14:15
  • +1 I'd never heard that argument before! Learn something new ... Commented Apr 7, 2015 at 14:18

Q: What is the subject of this sentence?
A: What is the subject of that sentence.

  • So it is? I don't understand your answer.
    – Droonkid
    Commented Apr 2, 2015 at 23:35
  • What is the subject of that sentence? What is the subject of that sentence. Commented Apr 2, 2015 at 23:35
  • Not the most helpful answer but I will accept it.
    – Droonkid
    Commented Apr 2, 2015 at 23:40
  • 1
    And who's on first then?
    – terdon
    Commented Apr 3, 2015 at 0:02
  • @terdon - I don't know.
    – Hot Licks
    Commented Apr 3, 2015 at 0:18

Chris Sunami wrote:

Q: What is the subject of this sentence? A: What is the subject of that sentence.

Yet, we have What are the subjects of this sentence? Therefore, the subjects of that sentence are "the subjects of this sentence".

In Chris Sunami's answer, "what" appears to be the predicative nominative (the subject of this sentence is what).

Neither the Cambridge dictionary and grammar, nor the Merriam-Webster mention "what" as a subject of a sentence. They define it as a pronoun, but all the examples they provide have it as the object of the verb. And that is confusing because there are plenty of cases where "what" is the subject:

What doesn't kill you makes you stronger

What boils in the pot?

What grows in the garden?

What is there to eat? (see this related question on SE)

and the sentence that troubled me:

We must keep what works and discard what doesn't

In other languages it is quite common to find "what" as the subject of a verb:

Was wuchs im Garten sehr gut? [German]

Cosa bolle in pentola? [Italiano]

That is why I was surprised that "what" in English is never mentioned as a subject in textbooks (but, to be honest, never explicitly forbidden either).

So I believe that yes, "what" can be the subject of your sentence.

EDIT 1: After posting this answer I noticed that MW has indeed two examples of "what" used as the subject:

What angered us was the tone of the article (entry 2.a)

Gave also, what is more valuable, understanding (entry 2.b)

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