1.whether和if均可用来引导主语从句，但if引导的从句不能位于句首。如： Whether they win or lose is all the same to me. 他们是赢是输於我都一样.（此时whether不能换作if ） Its doubtful whether therell be any seats left. 说不上还有没有空座位了. (此句whether能换作if) 2.whether和if均可用来引导宾语从句。如：I dont know whether/if I will be able to come.我不知道我是否能来. She asked me whether/if I was interested in working for her.她问我是否有兴趣为她工作。Well be told tomorrow whether we should take the exam or not.我们明天才知道是不是应该参加考试. I asked him whether he had done all the wo
