1、不定式前

I haven’t decided whether to leave or not.

2、介词后（宾语从句）

It depends on whether you want to do it or not.

3、名词后（同位语从句）

The question whether we’ll take part in the physics contest has not been discussed.

4、后面紧跟or not或or no时

I’ll come whether or not it rains.

5、可能造成歧义时

Please let me know whether you intend coming.

若用if可理解为：如果你想来，请告诉我一声。

6、主语从句在句首时

Whether they’ll go to Shaoxing is not known.

7、表示“无论”或“不论”时（让步状语从句）

Whether you like or not, you’ll have to do it.

8、引导表语从句

The question is whether we can finish the task on time.