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What’s the difference between if and whether?
If and whether are often interchangeable, but not always. Whether always refers to two possible alternatives, while if expresses several possibilities or a condition. A good general rule to follow is to use whether when you only have two choices, and use if in conditional sentences.
Read on for a detailed explanation of when to use if and when to use whether. Once you’ve mastered the difference, test out your knowledge in the free interactive exercises.
The cake is so tasty that Henry and Isabella would like to eat it all!
If they eat the whole cake, there won’t be any left to share with their friends later.
But Henry and Isabella don’t know if their friends are coming or not.
They can’t decide whether to save some cake.
If or whether?
Whether and if both indicate uncertainty. We use both words in reported speech and indirect questions. Sometimes these words are interchangeable:
- Henry asked Isabella if they should save some cake. ↔ Henry asked Isabella whether they should save some cake.
However, sometimes if and whether have different meanings:
- Isabella asked their friends whether they would come on Saturday or Sunday.
- two options: come on Saturday or come on Sunday
- Isabella asked their friends if they would come on Saturday or Sunday.
- if introduces a third option: come on Saturday, come on Sunday, or don’t come at all
If/whether … or not
When talking about two possibilities, we can add ‘or not’ to the end of the clause. This is not necessary, it is just for emphasis.
- Henry and Isabella don’t know if their friends are coming (or not).
- Henry and Isabella don’t know whether their friends are coming (or not).
Likewise, we can add ‘or not’ directly to whether. Again, this is generally redundant, but it is used in spoken English.
- It depends on whether or not their friends are coming.
The only time ‘or not’ is not redundant is when whether or not means regardless or no matter if. We cannot use if in the same way.
- They will eat the cake whether or not their friends come.
They will eat the cake if or not their friends come.
We can use if and whether in indirect questions. Whether can be more formal than if, and, as shown above, only expresses two possibilities.
- Henry asked Isabella if they should have some cake.
- Henry asked Isabella whether they should have some cake.
For more information about indirect questions, go to our page dedicated to indirect speech in English grammar.
- Use if in conditional sentences.
- If they eat the whole cake, there won’t be any to give their friends later.
- but not:
Whether they eat the whole cake …
For more information about conditional sentences see if clauses.
- Use whether before infinitives with to.
- They can’t decide whether to save some cake for their friends.
- but not: …
if to save some cake…
- Use whether after prepositions.
- The amount of cake they can eat depends on whether their friends come.
- but not: …
on if their friends come.
For more information about prepositions or infinitives with to, go to our page on prepositions or the infinitive/gerund section.