'if' vs 'whether'

Question

I have researched this on countless websites but am unable to understand a definitive distinction between 'whether' and 'if'. Are they basically interchangeable? See below.

I don't know if/whether/whether or not she's coming late.

Do all variants work? If not, is there a simple trick to always arrive at the right choice?

Thanks

Anonymous · Accepted Answer

The following are correct and have a similar meaning:

I don't know if she's coming late.

I don't know if she's coming late or not.

I don't know whether or not she's coming late.

I don't know whether she's coming late or not.

The following is ungrammatical:

I don't know whether she's coming late.

BarbaraPA · Answer

A rule that just about always work for you: If you can say "or not" then use "whether."

I don't know whether or not she's coming late.
I don't know whether she's coming late or not.
I don't know whether she's coming late. (I completely disagree that this is "ungrammatical.")

You certainly will hear and see "I don't know if she's coming late" and "I don't know if she's coming late or not."
Don't write or say this combination: "I don't know if or not she's coming late." -- You can use "whether" there, but not "if."

Another difference:
Whether you believe me or not, I saw aliens that night. -- You can't use "if" there. It could be "Even if you don't believe me,..."
Whether he drives me or not, I am still coming to your party. Even if he doesn't drive me, I'm still coming. (NOT: If he drives me or not, ...)

And of course, you use "if" for conditionals, but I don't think you are confused about that.

GPY · Answer

AnonymousThe following is ungrammatical:I don't know whether she's coming late.

I don't really agree with this. I think "or not" can be omitted and just implied.

Goronsky · Answer

Thanks, everybody.

RandomGuy · Answer

goronskyis there a simple trick

Yes. If it sounds right to you, then it’s right. It’s as simple as that.

(If the OP weren’t a native speaker, my answer would of course be very different.)

Deadrat · Answer

Mostly you'll get the same meaning whether or not you use "whether" or "not." Your last sentence isn't ungrammatical. The one variation you left out, however, is -- "I don't know if or not she's coming late." "Whether" may keep it's negative alternative close; "if" may not.

There are other preferences, as well. "Whether" precedes an infinitive and follows a preposition.

"I don't know whether to come late or not." OK
"I don't know if to come late." Not OK
"I didn't ask about whether she came late." OK
"I didn't ask about if she came late." Not OK

All the examples here are about a binary condition: she's late or she's not. A subtle distinction may arise when there are more than two choices because of what I'll call distributive doubt.

"I don't know whether she will arrive at 4 o'clock or 5 o'clock." This means the speaker believes there are two possible arrival times, but he doesn't know which one will obtain and which one won't. The doubt distributes to each.

"I don't know if she will arrive at 4 o'clock or 5 o'clock." This allows the possibility that the speaker has been given two alternative arrival times, but he doesn't know if either one will obtain. The doubt does not distribute and applies to both together, leaving open a possible (but unstated) 6 o'clock arrival time.

RandomGuy · Answer

deadratMostly...

I think our OP is more worried about violating prescriptive rules (as he often is) such as the one stated in this link, which says I don’t know if you will find this post helpful is incorrect. (Can you believe this nonsense was posted recently as an answer to the question of if vs. whether?)

Deadrat · Answer

Well, at least it was posted in a blog for people who think getting an MBA is good thing.

O, Lord! Save us from people who thought it was good idea to follow up a physics degree with one in religion, especially those who have to tell us they went to Harvard.

Amen.

Goronsky · Answer

A big 'thank-you' to everyone .. very appreciative.

Mike

'if' vs 'whether'

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