Why does "by whom" come first in a passive voice sentence?

active:- who broke this cup?
passive:- by whom was this cup broken?

In active voice who is subject and this cup is object then this sentence should start with object in passive like this:

passive:- this cup was broken by whom?

2 Answers 2


(In this answer, I loosely use the term "wh-phrase" to mean a phrase with a wh-word that defines what the question is about. If that phrase includes a preposition, it may in fact be a prepositional phrase, rather than having the wh-word as the head. Now on to the answer.)

In the standard form of every wh-question, the wh-phrase comes first. That's it.

It doesn't matter if that word is the subject, an object, a subject complement, an adverbial or anything else.

It also doesn't matter whether the sentence is active or passive.

Further, it doesn't matter what the subject or object are in the active equivalent of a passive sentence.

In all cases, the wh-phrase is first in the standard form of a question.

Who broke this cup? ("Who" = subject)
What did you break? ("What" = direct object)
What is this? ("What" = subject complement)
Where was the cup? ("Where" = adverbial)

To form a passive question, we start from the underlying passive statement

The cup was broken [by someone].

To make a question about "by someone", we first replace it with "by whom":

The cup was broken [by whom].

We then move this wh-phrase to the front of the sentence:

[By whom] the cup was broken ______.

Finally, we invert the subject and auxiliary verbs and add a question mark:

[By whom] was the cup broken?


(To the "Yeah, but what about" folks, I hear you, and yes, there are other ways to form this question, like leaving "by" at the end of the question and using "who" rather than "whom". But the OP hasn't asked about this, and there's no reason so far to think that's part of the issue, so no need to muddy the waters.)

  • 1
    You say that the wh-phrase always comes first, but in OP's question the first word is not a wh-word, but the word by, the phrase is a by-preposition phrase. In all your examples under "In all cases ...", the wh-word is first. I think readers deserve an explanation here - both of what a wh-phrase is and why by can appear first. Commented Nov 8, 2022 at 19:59
  • @Araucaria-Nothereanymore. I've added a description of my use of the term to the top.
    – gotube
    Commented Nov 8, 2022 at 21:08
  • "Yeah but" the OP specifically asks why the "By whom" comes first. This answer spends a lot of words on saying that it does come first (in the "standard form", whatever that means), and on how one might derive that form, but the OP seems already to know that. Inasmuch as this answer also acknowledges that the "by whom" does not necessarily come first after all, I'm having trouble seeing how it is responsive to the question actually posed. Commented Nov 8, 2022 at 22:25
  • @JohnBollinger "By whom" comes first for the same reason "Why" comes first in the OP's question -- that's the rules of question formation in English. The OP seemed to think it had something to do with subjects and objects or the passive and active voice, which is not the case. I answer the question in the first sentence. The rest of the answer is just expanding on that. Perhaps my answer would have been better as just that single sentence, but other than for word requests, I always expand at least a little bit.
    – gotube
    Commented Nov 9, 2022 at 5:43

I don't know of a rule stating that such sentences should start with the object.

Both of your passive sentences are grammatically correct.

The use of "whom" is uncommon in informal speech nowadays.

An angry giant in a fairy tale is more likely to shout, "By whom was this cup broken?" than "This cup was broken by whom?", which sounds somewhat calmer.

"To whom was it given?" and "It was given to whom?" are both correct.

Although we would usually ask, "What did you give her?" and "Where is your passport?", if we need confirmation we ask, "You gave her what?" and "Your passport is where?"

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