在英語學習中，好多同學對如何使用whether和if 感到模糊，常常誤用。下面我們分別來看一下whether和 if 的用法。
1 在表語從句和同位語從句中只能用whether表「是否」。
如：
He answered my question whether he would come .
The news whether our team has won the game is not known.
The question is whether the book is worth baying.
2 當主語從句位於主語位置上時，只能用whether表「是否」。
如：
Whether it will rain is not clear .
Whether they will come in time is a question .
3 在介詞後面引導賓語從句表「是否」，只能用whether。
如：
It all depends on whether they will support us .
The discussion focused on whether they would buy a new car .
4 後面直接跟動詞不定式時，只能用whether表「是否」。
如：
I don’t know whether to stay or not. .
如：
We didn’t know whether or not she was ready .
如：
Whether you like it or not ,you must do it well .
如：
Please let me know if you like it .
這個句子可有兩個意思：「請告訴我你是否喜歡。」或「如果你喜歡，請告訴我。」用whether就可以避免歧義。
如：
If it doesn’t rain tomorrow , we will go hiking .
If you like it , you can take it .
如：
Even if the job was difficult , they did it well .
Even if it’s sunny , it a bit cold .
如：
I wonder if / whether the news is true or not .
如：
He was not sure if / whether it is right or not .
3 主語從句中使用了形式主語it，主語從句後置時。
如：
It hasn’t been decided if / whether we shall have a class meeting .