whether, if 用法区别总结

if,even if,whether,unless,but for… 用法

       whether和if通用，都表示“是否”的意思。一般来说，后者比较正式，在口语中前者常用来代替后者。但两者有时具有不同的暗示。用whether时，正反两面的选择意义较强，问话人并不在意回答是肯定还是否定；而用if时，则比较强调单方面，即正面，问话人希望得到肯定的回答。另外，还要注意从以下六个方面的高频考点：

一、whether和if都可以与or not连用； 但whether和or not写在一起时，或在动词短语后，只能用whether，不能用if。如：

• I don't care whether (或if) it will rain or not．
• I don't  care  whether  or  not  it  will  rain.  (不用if)
• I don't  care  about whether  or  not  it  will  rain.  (不用if)

二、在引导宾语从句时，应注意：

1、表示“是否”时，两词都能引导宾语从句。

①I don't know whether/if I will be able to come.我不知道我是否能来.
②She asked me whether/if I was interested in working for her.她问我是否有兴趣为她工作。
③We'll 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.
 ④I asked him whether he had done all the work himself or whether he had had any assistance. 我问他这些工作都是他自己做的还是别人帮他做的.

⑤I wonder if/whether you can examine him now．
( 注意: 在两个供选择的从句之间若用or字, 则须重复whether一字. )

注:   ⑴当强调宾语从句并将其提前时只能用whether。
     如:Whether I'll have time to go with you I am not sure.我很难说我们是否有时间跟你们一起去。

2、宾语从句移置句首时，用whether，不用if。

Whether it is true or not， I can't say．

=I can't say whether/if it is true or not

3、宾语从句为否定形式时，通常用if，而不用whether。

I asked Tom if Mary  wouldn’t come．

4、动词discuss，decide, consider等后习惯上也常用Whether引导从句，不用if。
They discussed whether they should leave at once.他们讨论了是否应该马上离开。 
 We discussed whether the house should be sold.  我们讨论了这房子是否应卖掉。

We discussed whether we should buy the gift for him．

三、在下列情况下，只能用whether，不能用if。

1、与不定式连用时，只能用whether．

    He can't decide whether to accept or refuse．  

2、在介词后，只能用whether。

Everything depends on whether he is ready．  

I don't  care  about whether  or  not  it  will  rain.

3、在名词后作同位语时，只能用whether。   

The question whether they ought to stop working was discussed among the workers．

I have no idea whether he is there． 

4、引导主语从句时，只能用whether。

Whether  he comes or not doesn't concern me．

5、引导表语从句时，只能用whether。

What Maria doesn't  know is whether there will be enough snow．  

6、当whether和or not连用时，只用whether不用if。如:

I don’t know whether or not he will come.我不知道他是不是回来。
I'll be happy whether/if I get the job or not我能不能得到那份工作都一样高兴。注意：当or not放在whether引导的从句句尾，则可以用if来替换。
7、 当whether和or 连用表示明确的选择时，只用whether不用if。
He asked me whether I wanted to go there by train or by bus.他问我是想乘火车还是坐公共汽车去那里。
He hesitated about whether he should drive or take the train.他开车去还是坐火车去, 犹豫不决

注:whether 和or 连用还可以引导让步状语从句,此时也不用if。如：We'll go on with the work, whether we can find the necessary tools or not.

不管我们能否找到所需的工具,我们要把这件工作做下去。
Whether or not it rains / Whether it rains or not, we're playing football on Saturday.无论下不下雨, 我们星期六一定踢足球.

8、在动词不定式之前，只能用whether，不能用if。
①The question is whether to go to Munich or Vienna.问题是去慕尼黑还是去维也纳.
②She doesn't know whether to get married now or wait.是否现在结婚或是等待她不知道。
③We were wondering whether to go today or tomorrow.我们弄不清是今天走还是明天走.
④I'm not sure whether to resign or stay on.我拿不准主意是辞职还是留任.

四、if可引导条件状语从句，译作“如果”，whether可引导让步状语从句，译作“不管、无论”。

If I were you，I would not buy．

Whether he agrees or not，I shall go there．

We'll go on with the work, whether we can find the necessary tools or not.不管我们能否找到所需的工具,我们要把这件工作做下去。
Whether or not it rains / Whether it rains or not, we're playing football on Saturday.无论下不下雨, 我们星期六一定踢足球.

五、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。

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 ）
It's doubtful whether there'll be any seats left.说不上还有没有空座位了. (此句whether能换作if)

六、表语从句、同位语从句用whether引导不用if.

The doubt was whether you had broken the beautiful vase.疑问是你是否打坏了这只漂亮的花瓶。

The question whether we'll build another lecture building hasn't been settled.是否要另建一幢教学楼的问题还未决定。

七、强化练习：
1. The question has not been answered ____ Taiwan will be included on the Olympic torch relay route.
A．that          B．whether       C．which       D．if
2. You have not yet answered my question _____ I can join in the party tonight or not.   
   A. whether   B. if              C. that         D. which
3．— I d like to invite you to a party this evening.
— Thank you, but _____ I’ll be free I m not sure at the moment.
A. while                  B. if                      C. when        D. whether
4．---What are you anxious about?
    ---___________
A.      If we succeed   B.That we can succeed      C. Do we succeed   D.Whether we can succeed
5. Only when _____ the painting _____ decide ______the painting is worth buying.   

A. he sees, he can ,whether    B. does he see, can he,   if  
C. he sees, can he ,whether    D. sees he, he can,that
6. _____ English is his favourite subject
    A. I asked him if     B. I asked him that whether C. I asked him that     D. I asked him which
7. _____ they’ll go to the Summer Palace ____ the weather.
    A. If; depends on     B. Whether; depends upon   C. Whether; depended on     D. If; depended upon
8.It isn’t quite _____ ______ he will be present at the meeting.
    A. sure; whether     B. sure; if      C. certain; whether     D. certain; that
9. _____ the 2008 Olympic will be held in Beijing is not known yet.
    A. Whether     B. If     C. Whenever     D. That
10. No one was sure _____ he would be asked to speak next year.
    A. when     B. whether     C. what     D. how
11. It is still a question to us all _____ there is any living thing in some other places in the space.
    A. whether     B. which       C. what     D. where
12. I doubt _____ he will come here on time.

A. that     B. whether      C. when     D. where
13.    The point is not who said the words, _____ they are true or not.

A. but whether     B. and whether    C. but how     D. and how
14. “What did he ask you?” “_____ I would be late.”
A. That     B. When     C. Where     D. Whether
15. He treated all the people around him,______he knew or he didn't know,______.
     A. if, friendly                 B. whether, friendly
     C. if, in a friendly way      D. whether, in a friendly way
16. At the meeting, we discussed _____ we should employ more workers.
     A. if      B. whether    C. that     D.不填
Answers: BADDC ABCAB ABADD B