if和whether在名詞性從句中的用法

1、if 和whether在名詞性從句中的用法 whether和if都可以用作連詞，引導(dǎo)名詞性從句，表示“是否”。不同的是whether可以引導(dǎo)所有類型的名詞性從句；而if只能引導(dǎo)賓語(yǔ)從句和主語(yǔ)從句。賓賓語(yǔ)從句語(yǔ)從句 引導(dǎo)賓語(yǔ)從句既可以用whether，也可以用if，兩者?？梢曰Q。whether從正反兩個(gè)方面提出疑問(wèn)，選擇意義較強(qiáng)，多用于正式文體中；而if多用于口語(yǔ)，比較強(qiáng)調(diào)單方面，如： He asked me whether / if I could lend him my bike. Could you tell us whether / if it snows in winter in A

2、ustralia? She asked them whether / if they had gone there by car or by train.1. 在介詞后引導(dǎo)賓語(yǔ)從句只用在介詞后引導(dǎo)賓語(yǔ)從句只用whether。 lThis depends on whether we are determined to do it. lI am not interested in whether youll come or not. lIm thinking about whether well have a meeting. 4點(diǎn)例外點(diǎn)例外2.在及物在及物動(dòng)詞動(dòng)詞discuss，consider

3、等等后后的賓語(yǔ)從的賓語(yǔ)從句中，只能用句中，只能用whether。lWe discussed whether we should make a change in our plan. lWe were discussing whether we should take some measures.lWere discussing whether well go on a picnic. 3.賓語(yǔ)從句放在句首表示強(qiáng)調(diào)時(shí)，只能用賓語(yǔ)從句放在句首表示強(qiáng)調(diào)時(shí)，只能用whether 。lWhether it is true or not, I cant tell.lWhether you have met

4、 George before, I cant remember. 4. 引導(dǎo)一個(gè)否定的賓語(yǔ)從句，引導(dǎo)一個(gè)否定的賓語(yǔ)從句，只用只用if。whether不能用來(lái)引導(dǎo)否定的賓語(yǔ)從句，因?yàn)樗硎菊磧煞矫娴倪x擇意義比較強(qiáng)。lShe asked me if Tom didnt come. lHe considered if he shouldnt tell her the secret. whether/if 引導(dǎo)賓語(yǔ)從句 通?？梢曰Q（4點(diǎn)例外） 只用whether discuss等后 引導(dǎo)賓語(yǔ)從句放句首表強(qiáng)調(diào) 只用if： 介詞后引導(dǎo)否定的賓語(yǔ)從句1 I d like to invite you to

5、 a party this evening. Thank you, but _ Ill be free I m not sure at the moment. A. while B. if C. when 2-What are you anxious about? -_ A. If we succeed B. That we can succeed C. Do we succeed D. Whether we can succeed3. At the meeting, we discussed _ we should employ more workers. A. if C. that D.不

6、填D. whetherB. whether主語(yǔ)從句注意：注意： whether和和if均可引導(dǎo)主語(yǔ)從句，但均可引導(dǎo)主語(yǔ)從句，但if引導(dǎo)的從引導(dǎo)的從句不能位于句首。句不能位于句首。1. 引引導(dǎo)主語(yǔ)從句導(dǎo)主語(yǔ)從句并在句首時(shí)并在句首時(shí)只用只用whether。 Whether we go there is not decided. Its doubtful whether/if therell be any seats left. 引引導(dǎo)表語(yǔ)從句時(shí)只用導(dǎo)表語(yǔ)從句時(shí)只用whether。 l What we want to know is whether he will come to speak to

7、us tomorrow. lThe doubt was whether you had broken the beautiful vase. lThe question is whether we can get there on time. 表語(yǔ)從句表語(yǔ)從句 引導(dǎo)同位語(yǔ)從句時(shí)只用引導(dǎo)同位語(yǔ)從句時(shí)只用whether。 The question whether well build another lecture building hasnt been settled. The question whether hell come is unknown. We must consider the

8、 question whether we will take these measures.同位語(yǔ)從句同位語(yǔ)從句Exercises 1. The question has not been answered _ Taiwan will be included on the Olympic torch relay route. Athat Cwhich Dif 2. _ theyll go to the Summer Palace _ the weather. A. If; depends on B. Whether; depends upon C. Whether; depended on D

9、. If; depended uponBwhether1. 直接與直接與or not連用時(shí)只用連用時(shí)只用whether。 lI dont know whether or not he will go. lIm not sure whether or not they will come for our help. 【注意】若whether和or not不連在一起，在口語(yǔ)中可以用if取代whether。例如： lI am not certain whether/if the train will arrive on time or not. lI dont care whether/if you

10、r car breaks down or not. 其他情況（其他情況（3點(diǎn)）點(diǎn)）2. 在動(dòng)詞不定式之前，只能用在動(dòng)詞不定式之前，只能用whether。lHe doesnt know whether to stay or not.lShe doesnt knows whether to get married now or wait. 3. 當(dāng)用當(dāng)用if會(huì)引起歧義時(shí)只用會(huì)引起歧義時(shí)只用whether。if除引導(dǎo)賓語(yǔ)從句外，還可以引導(dǎo)條件狀語(yǔ)從句，作“如果如果”解。Please let me know if you intend to come.A：if引導(dǎo)賓語(yǔ)從句,“請(qǐng)讓我知道你是否想來(lái)?！?B：if引導(dǎo)條件狀語(yǔ)從句,“如果你打算來(lái)，請(qǐng)讓我知道?！?Please let me know whether you intend to come. EX: Let me know if he has left for Shanghai. 請(qǐng)告訴我他是否已經(jīng)去上海了。如果他已經(jīng)去上海了，請(qǐng)告訴我一聲。 Let me know whether he has left for Shanghai. Summary賓語(yǔ)從