Language/English/Grammar/When-use-If-or-Whether

When to use "whether" or "if" in English?

Use "if" or "whether" (Interchangeable):

Whether and if can be used interchangeably in the following circumstances:

When reporting yes/no questions.

I am not sure whether I will be attending the event. I am not sure if I will be attending the event.

(In this example, the yes/no question is "Am I attending the event?")

In whether/if...or...constructions. I would like to know whether it is a true story or fabricated. I would like to know if it is a true story or fabricated.

Note: Using whether is far more common. It is certainly more formal.

Use only "if" with:

the conditional tense

A sentence that can only be realized under certain conditions.

• Bob didn’t know if Amanda was going away.

Use only "whether" when

Verb with "to"

• Bob didn’t know whether to invite Amanda to the party.