I have read many articles, but I don't know why often the verb "discuss" is followed by the conjunction "whether," but not "if". Do you confirm that this verb is an exception and after that we have to use always "whether"? In other words as an example I believe that:

  • We were discussing whether to leave early (or not). Correct
  • We were discussing if to leave early (or not). Incorrect

3 Answers 3


It's not the verb discuss that makes the second sentence ungrammatical: *We were discussing if to leave early (or not). It is the infinitive (which is, in our case, to leave).

According to Practical English Usage (by Michael Swan),

621 whether and if
3 infinitives
Whether, but not if, is used before to-infinitives.
  They can't decide whether to get married now or wait.
  (NOT They can't decide if to get married ...)

  • For the rest of whether/if usage, see ell.stackexchange.com/a/22288/3281. (This is mainly for others. I think the OP knew it already.) May 1, 2014 at 10:03
  • Interesting. I have not looked at this topic like this @DamkerngT. Hope natives confirm this idea over this specific example of mine. :) Anyway still I think after some certain verbs (for instance, discuss,) it is not possible or rather grammatical to use "if".
    – A-friend
    May 1, 2014 at 10:14
  • 1
    It's possible, but not common; you could say "we were discussing if it would be okay to leave early", for example.
    – Hellion
    May 1, 2014 at 17:19
  • @Hellion But that's an ordinary finite-verb clause, not an infinitive. May 1, 2014 at 17:48
  • @StoneyB, yes, but my point is that the mere presence of "if" does not mean you cannot use it after "discuss", as A-friend was wondering in the comment above.
    – Hellion
    May 1, 2014 at 17:52

Using if after (some form of) discuss is certainly possible. You could say, for example:

We were discussing if it's okay to leave early.

I would claim that it's more natural to say whether there, but if is also acceptable.


Whether should be used not if. The test for whether you can use if is called the inversion test.

Take the sentence "We'll go to the beach if it's sunny." This sentence can be inverted to say "If it's sunny, we'll go to the beach," with no loss of meaning.

In the sentence "We were discussing if it's okay to leave early," the inversion produces a nonsensical statement: "If it's okay to leave early, we were discussing."

Accordingly whether should be used not if.

  • 1
    The sentence "We were discussing if it's okay to leave early" is probably a poor example of this, because if it's okay to leave early is a projected clause; the reported speech means that you can use it in that way.
    – jimsug
    May 17, 2014 at 16:21

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