There is an online English class room which has an increasing number of teachers, most of whom I don't know at all.

I have to book a room by time, e.g. 8 pm Wednesday, to attend class. I don't know who will be assigned to that classroom before I booked a room successfully.

To convey the same idea, should I say

I don't know which teacher will be assigned to me

I don't know what teacher will be assigned to me

  • The fact that the number is increasing makes no difference to the use of which or what. You could have a million teachers, and which would still be appropriate. The general criteria is that when you use which, you are referring to one out of an identified set of things (of any size); when you use what, you are referring to something in general, which isn't specified as coming from an identified set of things. Commented May 30, 2020 at 15:11
  • Think of it this way: if you are envisioning a particular group of people or things in the context of using the sentence, then which is generally more common; otherwise, it would be what. Commented May 30, 2020 at 15:14
  • 1
    @JasonBassford That is a wrong duplicate target about relative pronouns. This question is about determiners.
    – Eddie Kal
    Commented May 30, 2020 at 15:31
  • @JasonBassford That reminds me of a comment at that link. Phone numbers are a large, but limited set. You don't say "which is your phone number." Commented May 30, 2020 at 15:40
  • @JackO'Flaherty You do if you hand somebody a phone book before asking. Commented May 30, 2020 at 19:30

1 Answer 1


"Which" is more appropriate for referring to one of a known small set, for example, "There are five teachers. I wonder which of them will be assigned." I think "what teacher" fits the situation you describe.

  • Thank you. Actually, there are more than 10,000 teachers there, is it still appropriate to use "which"?
    – PutBere
    Commented May 30, 2020 at 7:04
  • As I said, I would use "what", not "which". Commented May 30, 2020 at 16:31

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