Is it standard to use "what" as a form of "which," such as in the sentence:

The tour guide let us know what items were permitted to be taken along on the trip.

In this instance I prefer "what" because it refers to categories of items as opposed to specific items.

  • In this example, what is not a form of which*. The two words give different meanings to the sentence. You may need to set aside that presumption and then work on understanding the difference. – Kris Jun 28 '13 at 6:42
  • @FumbleFingers That reference is highly recommended reading for the OP. However, the presumption that what is being used here as a "form" of what is incorrect. – Kris Jun 28 '13 at 6:43
  • @Kris: I don't see what you mean. OP's context is identical to "Tell me what books I need", which so far as I'm concerned can only ever mean the same as "Tell me which books I need". My own usages here can't be switched, obviously, but the ones in my quoted examples are simply stylistic choices (though overwhelmingly, people tend to choose what in both mine and OP's examples). – FumbleFingers Jun 28 '13 at 13:55
  • @FumbleFingers Your inference is respected. However, see also my first comment, which incidentally is at variance with the opinion you hold. – Kris Jul 1 '13 at 6:12
  • @Kris: I really don't see what you mean. You say "the two words give different meanings", but I don't know what different meanings you're thinking of. It seems to me OP's sentence means the same regardless of whether it uses which or what. – FumbleFingers Jul 1 '13 at 15:53

Nice question! I had always thought that one would use "which" if one were listing items from a list, including a phrase which would if expanded become a list, and use "what" for that not in a list, or expandable as such. My examples:

  • The tour guide let us know which items we were permitted to bring on the trip.
  • Wisdom dictates which actions to take and which to avoid.


  • The tour guide let us know what to expect on the trip.
  • The police officer told me what to do.

I may be completely off, it wouldn't be the first time, but it seems right to me.

  • So in my example sentence, you would say that "what" is inappropriate? In that case, too, the items are not necessarily part of a clearly defined list; e.g., the instructions might be not to bring anything sharp or flammable. – kurkevan Jun 27 '13 at 20:54
  • No, I would not say "inappropriate"! If I were an English teacher and your sentence came across my desk as part of an essay, I wouldn't mark it incorrect at all. I am merely saying that "my way" is measurably more precise. I am not the Imperial Arbiter of English Style and Usage. LOL. That would be William Strunk and E. B. White, but they never weighed in on this subject, so I have expressed my opinion, humble as it is. Your preference is perfectly grammatical, never fear. – Cyberherbalist Jun 27 '13 at 21:03
  • You see, "what items are permitted" would, if expanded, turn into a list. Items are inherently listable. "Which" implies granularity; "what" implies a general messy splat. I hope I am not making myself unclear. – Cyberherbalist Jun 27 '13 at 21:05
  • No, I understand what you mean. Thanks for your answer. – kurkevan Jun 27 '13 at 21:07

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