ifwhether用法

If/whether的区别

1.whether和if都可以引导宾语从句，表示“是否”，在口语或间接引语中两者可以互换使用。如：

I wonder if / whether I can get some advice from you.

Ask him whether / if he can come.

2.但在有些情况下，whether和if的用法有一定区别

1. whether引导的从句常可以与连词or或or not直接连用，而if一般不能。如：正：Let me know whethe r you can come or not.

误：Let me know if you can come or not.

2. 当宾语从句提到句首时，只能用whether引导，而不能用if。如：

正：Whether it is true or not, I can’t tell.

误：If it is true or not, I can’t tell.

3. whether可以引导带to的不定式，if则不能。如：

正：I don’t know whether to accept or refuse.

误：I don’t know if to accept or refuse.

4. whether及其引导的成分可放于介词之后，作介词的宾语，但if不能。如：正：I worry about whether I hurt her feelings.

误：I worry about if I hurt her feelings.

5. whether可以引导从句，作主语、表语或同位语，而if不能。如：

正：It was uncertain whether he would come.

误：It was uncertain if he would come.

正：His first question was whether Tom had arrived yet.

误：His first question was if Tom had arrived yet.

正：We must consider the question whether we will take these measures.

误：We must consider the question if we will take these measures.

3.whether 和if 可以互换吗？在哪些情况下可以呢

下面的几个情况可不可以？

1."Have you seen the film?" He asked me.

→he asked me whether I had seen the film.

2."You've already got well, Haven't you?" she asked.

→she asked whether I had a already got well.

3.He asked, "Are you a Party member or a League member?"

→He asked me If I was a Party member or a League member,

这三个都做“是否”讲是可以互换的

4.下面的情况不能互换：

1．Whether可以与or not 连用构成whether…or not或者whether or not，但if 一般没有这种用法。

2．如果宾语从句是否定结构，则用if，而不用whether。

3．介词的宾语从句只能用Whether引导。

4、引导主语从句、表语从句、同位语从句时都用whether。

5．Discuss 或decide 等动词后，通常只跟whether引导的宾语从句，而不跟if 引导的宾语从句。

6．Whether后面可以接不定式短语，而if不能。

7．在主从复合句中，为避免产生歧义，不用if而用whether，而使意义更加明确。