if与whether用法区别

if与whether用法区别
收集整理：王俊尧
1.下列情况只能用whether：
（1）直接与or not连用时,往往用whether(if…or not也可以使用)。

如: Let me know whether or not he will come.
(= Let me know whether / if he will come or not.)
让我知道他是否能来。

I don't know whether or not he does any washing.
(= I don't know whether / if he does any washing or not.)
我不知道他在家洗不洗衣服。

I wonder whether we stay or whether we go.
我想知道我们是去还是留。

(2) 在介词之后用whether。

如：
I'm interested in whether he likes English．
我关心的是他是否喜欢英语。

We're thinking about whether we can finish the work on time．
我们正在考虑是否能按时完成这项工作。

I worry about whether I hurt her feelings．
我担心是否伤了她的感情。

(３)在不定式前用whether。

如：
He hasn't decided whether to visit the old man．
他尚未决定是否拜访那位老人。

I don't know whether to go．我不知去否。

He hasn't decided whether to go by bus or by train．
他还未决定是乘公共汽车去还是坐火车去。

（４）whether置于句首时，不能换用if。

如：
Whether this is true or not，I can't say．
这是否真的我说不上来。

（５）引导主语从句和表语从句时宜用whether。

如：
Whether she will come or not is still a question．
她是否能来还是个问题。

The question is whether we can catch the bus．
问题是我们能否赶上公共汽车。

（６）若用if会引起歧义时，则用whether。

如：
Please let me know if you like the book．可理解为：
a．Please let me know whether you like the book．
请告诉我你是否喜欢这本书。

b．If you like the book，please let me know．
你如果喜欢这本书，请告诉我
2. 如果宾语从句是否定式，就只能用if引导。

如：
Ｉdon’t care if it doesn’t rain.
我不管天是否不下雨。

3. 如果宾语从句原来是特殊疑问句，只需用原来的疑问词引导。

但一定要注意从句的语序是陈述语序，时态与主句相呼应，句尾标点符号取决于主句。

如果主句是问的就用“”，是陈述的就用“．”。

如：
Where will we have the meeting this afternoon Could you tell me →
Could you tell me where we will have the meeting this afternoon
你能告诉我我们今天下午将在哪儿开会吗
Ｗho bought the present for meI don't know．→
I don't know who bought the present for me.
我不知道谁给我买了礼物。

４．当一个特殊疑问句本身就是陈述语序（即“主＋谓＋（宾）”或“主＋系＋表”结构），将其变为间接引语（即宾语从句）时，无需改变语序。

例如：
What’s the matter with him She as ked me. →
She asked me what was the matter with him.
Who looks after your grandfather He asked me. →
He asked me who looked after my grandfather.
5. 当主句的谓语动词是think (认为), know（知道）, believe（相信）, suppose（料想）, guess（猜想）等表示看法的词时，有下列两种情况：
（1）如果主句的主语是第一人称，后接的宾语从句的否定词通常要移动到主句中，即否定主句动词，这种形式称为“否定的转移”。

这种前置否定的宾语从句要变成反意疑问句时，疑问部分的主、谓语要与从句一致。

如：
He isn’t a student . I think. →
I don’t think that he is a student, is he
She can’t do that. We suppose. →
We don’t suppose that she can do that, can she
(2)如果主句的主语是第二三人称时，否定词通常不转移，但它的反意疑问句的主、谓语应与主句一致。

如：
He thinks he can’t go with you, does he
She thought she couldn’t do that this afternoon, did she
6. 当主句的谓语动词是think (认为), know（知道）, believe（相信）, suppose（料想）, guess（猜想）say（说），imagine（想象）等表示看法的词时（know除外），如果引导宾语从句的是特殊疑问词，且是疑问句时，要将特殊疑问词放到句首。

即，
特殊疑问词+do you think／say/…+ 从句．如：
(1) Do you say how old he is (×)
How old do you say he is (√)
(2) Do you think what is the fastest way to travel (×)
What do you think is the fastest way to travel (√)
(3) Do you suppose what he wanted (×)
What do you suppose he wanted (√)
7. it作形式宾语的情况
常用句型为：think/believe/find/feel + it + adj. / n. + that从句。

如：
I think it possible that he hasn’t come.
我认为他没有来是可能的。

I feel it easy that he studies English well.
我发现他学习英语是容易的。

I feel it your duty that you serve the people.
我觉得为人民服务是你的职责。

注：本资料属于收集整理，如若有误，诚接批评指点。

谢谢！。