Confusing words: Whether or if?

"Police are probing WHETHER the deaths of a woman, 107, and her daughter are a murder and suicide." (The Mirror, 12 Apr 2013)

" 'I didn't know WHETHER to laugh or cry'- Twitter responds to Lindsay Lohan on Charlie Sheen's Anger Management." (The Independent, 12 Apr 2013)

I don't know whether or not I should...

 

There are often doubts regarding the use of "whether", especially among learners up to B1 level.

WHETHER /ˈwɛðə/ is a conjunction used when we're expressing a doubt or choice between alternatives.

In indirect questions which expect a yes/no answer, we can either use whether or if.

I asked them whether/if they were going to take the exams in June.

If or appears later in the sentence, we generally prefer whether, although if is also possible.

They weren't sure whether/if she was telling the truth or not.  

Whether and not if is used in the following conditions:

Before an infinitive 

They can't decide whether to take the exams in June.

After a preposition

The students were unsure about whether the teacher's explanation was helpful. 

Immediately before "or not"

I'm not sure whether or not the students are ready.  

Contrast with: I'm not sure whether/if the students are ready or not. 

Spelling 

Don't confuse the spelling of the conjunction whether with the noun weather. 

Both are pronounced the same: /ˈwɛðə/