Whether is used when someone does not know which of the two possibilities is true.
- She asked me whether I was married.
- I don’t know whether she will come.
- I asked whether she had received the letter.
Whether … or… is often used as a double conjunction.
- She doesn’t know whether her son is dead or alive.
- I don’t know whether the answer is right or wrong.
Whether is also used to suggest that it doesn’t matter which of the two possibilities is true because the situation will remain the same.
- Whether we go by road or rail, the journey will take at least four hours.
Whether… or not
- Jenny is going abroad whether she likes it or not.
- Jenny is going abroad whether or not she likes it.
Whether and if
Both whether and if can be used to introduce indirect Yes/No questions.
- She asked if I liked English films. OR She asked whether I liked English films.
Before an infinitive, we use whether. If is not possible in this case.
- I can’t decide whether to accept that job. (NOT I can’t decide if to accept that job.)
After a preposition, use whether.
- There are doubts about whether the judgment was fair.
Whether can be followed by ‘or not’. If is not possible in this case.
- The question is whether or not we have the right to interfere. (NOT The question is if or not…)
Both whether and if are possible when ‘or’ appears later in the sentence; however, whether is considered more correct.
- It is not clear whether the source of information is reliable or not. (Formal)
- It is not clear if the source of information is reliable or not. (Very informal)