英语语法：64 If Versus Whether（在线收听）

Grammar Girl here. Today's topic is whether--not rain or sunshine, but whether w-h-e-t-h-e-r, as in whether you like it or not, it's the topic.

[Listener question about if versus whether and whether you need an or not after whether]

Well, it's been a while since the listener called in those questions, so I hope people are speaking to each other by now. But they are great questions.

First, let's figure out when to use whether and when to use if.

If Versus Whether

Although in informal writing and speech the two words are often used interchangeably, in formal writing, such as in technical writing at work, it's a good idea to make a distinction between them because the meaning can sometimes be different depending on which word you use. The formal rule is to use if when you have a conditional sentence and whether when you are showing that two alternatives are possible. Some examples will make this more clear.

Here's an example where the two words could be interchangeable:

Squiggly didn't know whether Aardvark would arrive on Friday.

Squiggly didn't know if Aardvark would arrive on Friday.

In either sentence, the meaning is that Aardvark may or may not arrive on Friday.

Now, here are some examples where the words are not interchangeable.

Squiggly didn't know whether Aardvark would arrive on Friday or Saturday.

Because I used whether, you know that there are two possibilities: Aardvark will arrive on Friday or Aardvark will arrive on Saturday.

Now see how the sentence has a different meaning when I use if instead of whether:

Squiggly didn't know if Aardvark would arrive on Friday or Saturday.

Now in addition to arriving on Friday or Saturday, there is the possibility that Aardvark may not arrive at all. These last two sentences show why it is best to use whether when you have two possibilities, and that is why I recommend using whether instead of if when you have two possibilities, even when the meaning wouldn't change if you use if. It's safer and more consistent.

Here's a final pair of examples:

Call Squiggly if you are going to arrive on Friday.

Call Squiggly whether or not you are going to arrive on Friday.

The first sentence is conditional. Call Squiggly if you are going to arrive on Friday means Aardvark is only expected to call if he is coming.

The second sentence is not conditional. Call Squiggly whether or not you are going to arrive on Friday means Aardvark is expected to call either way.

So to sum up, use whether when you have two discrete choices or mean "regardless of whether," and use if for conditional sentences.

Whether Versus Whether or Not

That last example is also a good lead in to the second part of the caller's question: when do you need an or not after whether? Why did I say, "Call Squiggly whether or not you are going to arrive on Friday"?

Often, the or not is just extra fluff and should be left off. In my first example, where I said, "Squiggly didn't know whether Aardvark would arrive on Friday," adding an or not wouldn't change the meaning or emphasis. Squiggly didn't know whether or not Aardvark would arrive on Friday means the same thing as Squiggly didn't know whether Aardvark would arrive on Friday. Or not is superfluous, so leave it out.

On the other hand, you need the full phrase whether or not when you mean "regardless of whether." It shows that there is equal emphasis on both options.

Call Squiggly regardless of whether you are going to arrive on Friday.

Call Squiggly whether or not you are going to arrive on Friday.

Finally, a listener wrote to say that her boss was driving her crazy by saying "rather or not" instead of "whether or not." So I'll add that "rather or not" is incorrect; whether is a conjunction and rather is an adverb, and they are not interchangeable. "Whether or not" is the correct way to show that there are two possibilities or you mean "regardless of whether."

Questions and comments for me go to...or the voicemail line at 206-338-GIRL. You can also read the full transcript of this podcast at quickanddirtytips.com, where you can leave comments and check out the other great podcasts. We've launched a new show I expect you'll all like called the Make-It-Green Girl, so check it out.