Quick English: Using Whether vs. If
Formally, "if" and "whether" are used in very specific examples, and give sentences different meanings.
Whether vs. If
Use "if" when you have a conditional sentence. (That's a sentence that can only take place once a specific action has occurred.)
Charlie didn't know if Alice was going away for the weekend.
Use "whether" when you are showing there are two possible outcomes.
Charlie didn't know whether Alice was going to the beach or the mountains for the weekend.
You can use either "whether" or "if" when...
One outcome is unspoken, but understood, such as in indirect questions.
> Alice was going away on Friday.whetherCharlie didn't know
> Charlie didn't know if Alice was going away on Friday.
In this example, the phrase "or not", is understood. So, Alice may not go away on Friday. Because the second option doesn't need to be said, you can use "whether" or "if".
Only "whether" can be used when...
There is an infinitive with "to".
> Charlie didn't know whether to invite Alice to the party on Saturday.
Saying "He didn't know if to invite Alice" just doesn't work. There is a preposition beforehand.
> Charlie wanted to have a conversation with Alice about whether she was away for the weekend.
Using the word "or".
> Charlie didn't know whether to call or text to find out about her plans.
When the clause beginning with a conditional is the subject of the sentence.
> Whether Alice can come or not depends on whether her boss will let her have the day off work.
English Grammar Activity
Should you use "whether" or "if" in the following sentences, or can you use either? For answers, see the Answer Key.
1. Did you find out _____ Alice was away this weekend?
2. ______ she can't make it, will you still have the party?
3. "I don't know ________ or not the weather will be nice enough for the beach," Alice said.
4. I need to know _________ to mention the party to Alice or not.
5. _________ Charlie invites me to the party, I'll attend.