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Can I use “what” instead of "which" in this sentence? Why or why not?

My first reaction is that using "what" is not very proper here, but I can't tell why. I find it a little tricky on using “what” in sentences like this.

  • 1
    A related question: Which vs. What Jan 12, 2015 at 3:49
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    Is that "which" word a relative word or an interrogative word? That can often appear to be somewhat difficult to figure out, at times. Maybe someone can show us which it is, or if it could be ambiguous, or whatever? :)
    – F.E.
    Jan 12, 2015 at 5:51
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    I'm over my head for sure, but by my lights, which is not a pronoun at all here. If it's a relative pronoun, doesn't it need an antecedent? If it's a pronoun at all, doesn't it need to replace or stand for a noun or noun phrase? If so, what noun does it stand for? As a word class issue, I think which is an adjective here, modifying materials, or could be considered by some a determiner(?) Jan 12, 2015 at 6:03
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    There is a relative "which" that is a determinative word, but then those only occur in supplementary relatives (but there is no supplementary relative clause in the OP's example). So, my vote is for interrogative word. (CGEL page 1048)
    – F.E.
    Jan 12, 2015 at 7:47
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    which is much more elegant in the sentence. The use of which or what is often said to be analogous to using 'the' or 'a', that is, making a definite reference or an indefinite one. Do you want the materials, or do you want some materials.
    – user6951
    Jan 12, 2015 at 8:08

2 Answers 2


Both versions would be correct grammatically and idiomatically, though I personally prefer which.

Which is generally used when selecting from a number of items in a group. Here we are choosing from a variety of potentially suitable materials. If you are presented with a limited set of choices and asked to choose one, which is strongly preferred.

What is more open; it allows you to select from a much broader range of options. If you are presented with a broad choice, what is preferred. What is the only option when no limits have been placed on the choice.

Ex: My wife and I are trying to decide what we want to do with our weekend.

Me: What would you like to do today?

In this sentence what is the only option. Without some (even poorly defined) set of possible choices, which does not make sense.

Ex: I am at a restaurant with my wife and we have just started looking over the menu.

Me: What do you think you'll order? (broad range of choices)
Wife: I'm not sure, the fish and the chicken both look good to me. Which would you pick? (narrow range of choices)

In my statement, what is the proper word, as all options are available. Using which here would be confusing (though perhaps I could accompany it with a gesture toward the choices on the menu and force it to make sense.) In my wife's statement, either which or what is appropriate, though which would be preferable. Moreover, if my wife used what here, she might be asking my opinion from the entire menu, whereas which limits my response to either chicken or fish.

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    It's like choosing whether to make an indirect reference or a direct reference. See my comment under the question. The property of 'poorly defined' corresponds to that of an indefinite reference.
    – user6951
    Jan 12, 2015 at 8:14

Yes, you can use what instead of which in that sentence. One of the major meanings of what is:


  1. Which one or ones of several or many: What college are you attending? You should know what musical that song is from.


Confusion here is to be expected, because it is common to use what in ways that are nonstandard when which or who would be standard, more commonly in British English speech: It was that what got us in trouble.

Also, there are some conventions and patterns that many experienced (maybe we can say skilled) writers use to sometimes determine that one of these words is better stylistically, but few such writers could (accurately) explain why, because the large number of factors that can be involved in making such decisions render the decisionmaking process too complex to explain (or learn) consciously.

For example, I would choose which in your quoted sentence. What is also fine. But I don't think I can explain why in a way that many other "experienced" or "skilled" writers would agree with.

Another source of confusion is there are many "rules" related to this kind of question which people (including me) may have "learned" from one source or another, and we may feel strongly that one or the other is correct or incorrect. Very often, there is no authentic reason to proclaim such "rules" as authoritative, universal, or non-arbitrary.

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    Yeah, you are quite right in talking about the latent language conventions and personal stylistics. For example, to me, for no reason, it doesn't sound that pleasing or natural with a "what" instead of the word "which" in the op sentence.
    – dennylv
    Jan 12, 2015 at 4:18
  • Right. Though instead of for no reason, probably for reasons we cannot articulate, or confidently articulate, or completely articulate. It's like asking a composer why they chose a particular chord in a particular place in a piece of music. Why a dancer rotated her left leg 42 degrees while tilting her head back instead of forward, etc. Sometimes we know, sometimes we sorta know. Often we have no idea. And very often, we invent incorrect explanations. Jan 12, 2015 at 4:32
  • Yet the rationale behind the choice of whether to use which or what in this context can be stated concisely. And it explains what native speakers do unconsciously. That is what genuine grammar rules do, they describe how people use a language.
    – user6951
    Jan 12, 2015 at 8:05
  • Can be stated concisely, but who has decided that any such statement is "correct"? And if some "authoritative" or "knowledgeable" person, organization, or publication disagrees? Jan 12, 2015 at 9:38

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