Can I use the word "whether" instead of "which" as in the following sentence?

"How to Decide Whether to Use Product A or Product B" (this is a heading)

I would usually write it as "How to Decide which to Use: Product A or Product B" or just "When to Use Product A or Product B".

If the first example with "whether" is acceptable, in what situation is it more suitable than other two ways of suggesting options?


Just as where is the wh-word that goes in front of questions about location, whether is the wh-word that goes in front of yes/no questions when they're subordinated:

  • Is he going (or not)? ~ I wonder whether he's going (or not).

Since yes/no questions imply a binary choice, a conjoined or not phrase may often be added.
For the same reason, embedded question complements headed by whether can often use if instead:

  • I wonder if he's going (or not).

Unlike other wh-words, whether is never used to mark a regular question:

  • *Whether is he going?

because yes/no questions already do that without a wh-word.

  • Is he going?

In this case, whether can introduce two conjoined infinitive clauses

  • whether for me to buy sugar puffs or whether for me to buy coco pops

reduced by conjunction reduction by deleting the optional boldface above, to

  • whether to buy sugar puffs or coco pops

So it's fine provided it is introducing a yes/no question or some binary opposition.

  • 1
    +1 Useful post. Might be worth mentioning that the or not being mandatory only applies if the clause is functioning as a conditional adjunct. (... Or it might not). – Araucaria Dec 12 '16 at 10:18
  • 2
    Thanks. I corrected the ambiguous sentence; or not phrases are never mandatory, always optional. – John Lawler Dec 12 '16 at 14:49
  • Thanks for the enlightening answer. This addresses a question that was on my mind, which is, whether it is always acceptable to substitute "if" for "whether". Can you think of any examples where this wouldn't be the case? – ktm5124 Dec 12 '16 at 15:33
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    Well, the first example sentence has a Wh-infinitive construction, whether to use Product A or Product B. Wh-words can take infinitive complements, but if can't: *if to use Product A or Product B. – John Lawler Dec 12 '16 at 15:43
  • 1
    @John Just a minor note: the or not phrase is mandatory when the whether clause indicates the applicability of the main clause regardless of which outcome is true, e.g., “You’re coming whether you like it or not”; leaving it out and saying just, “You’re coming whether you like it” would be, if not ungrammatical, then at least highly unusual. – Janus Bahs Jacquet Aug 10 '18 at 15:36

You seem to have grasped the usage quite well.

The following two sentences mean exactly the same thing:

  1. I must decide which to buy: sugar puffs or coco pops.

  2. I must decide whether to buy sugar puffs or coco pops.

  • 3
    I'd use a colon. – Edwin Ashworth Nov 7 '14 at 8:50
  • Thank you WS2 for the advice, and also Edwin for pointing out the use of colon. Which one would you guys use for my example: which or whether? – Jun Kyoto Nov 10 '14 at 0:16
  • @user77176 Probably the second, unless it made for a long and complicated sentence that was difficult to follow - it is not always simply about sugar puffs and coco pops! – WS2 Nov 10 '14 at 1:24
  • 1
    @EdwinAshworth Quite right. Duly amended. – WS2 Nov 10 '14 at 1:25

Which is the clear favorite if you have more than two choices or if you do not want to list all of the choices. As other answers note, whether implies a binary choice.

Imagine you are going to get a kitten, and you get to pick from a litter of nine kittens. Which sounds better?

I don't know which kitten to bring home.
I don't know whether to bring home the white one, or the spotted one, or the calico one, or the runt, or the tabby-looking one...

The first is unmarked, the second means that you are violating Grice's maxim of brevity (and are therefore communicating something in addition to your hesitation at choosing).


Whether implies a choice to be made and focuses on the question as a whole, and usually involves two options, even if one is to not make a choice.

Which means pick from available (known) options.

They are not interchangeable in the sentence without also adjusting punctuation.

  • SrJoven, thank you for your comment. Unfortunately I have not grasped the difference between the two from your explanation... "choice to be made" and "pick from available options" seem the same to me. Which one would you use for my example? – Jun Kyoto Nov 10 '14 at 0:14
  • I'm not sure how better to explain it. You didn't ask me Whether one would you use...?. Why not? Because you asked me to pick (exactly one choice) from a list. If you asked me Whether I should A or B? It would be different. But before asking which vs whether, look in a dictionary, and find out what still is unclear to you. – SrJoven Nov 10 '14 at 0:27
  • Hi SrJoven, I was misreading your comment. Sorry and thank you for your patience. – Jun Kyoto Nov 10 '14 at 3:54

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