一、作主語，可以用it代替，it叫形式主語，動(dòng)詞不定式放在后面叫真正主語
1．To learn a foreign language is not easy.
It is not easy to learn a foreign language.
2. It’s dangerous to drive very fast.
二、作表語
My idea is to ring him up at once. 我的想法是馬上給他打電話。
如果主語部分含實(shí)義動(dòng)詞do，且作表語的動(dòng)詞又是“do”的內(nèi)容，這時(shí)表語不定式的“to”可以省略。如：All I did was wait here. 我能做的就是在這里等。
三、?？山觿?dòng)詞不定式作賓語的動(dòng)詞有：agree(同意), hope(希望), decide(決定), need(需要), mean(打算), wish(希望), fail(失敗), want(想要), begin(開始), would like(想要)等。
He has decided to go to the countryside. 他已決心去鄉(xiāng)下。
四、“疑問詞 + 動(dòng)詞不定式”結(jié)構(gòu)可以作動(dòng)詞know、think、find out等的賓語。
I don’t know who to ask. 我真不知道該問誰。
五、“疑問詞 + 動(dòng)詞不定式”可以作動(dòng)詞show、teach、ask等后面的直接賓語。
She told me where to find the earphone. 她告訴我什么地方可以找到耳機(jī)。
六、如果賓語太長(zhǎng)，可用it作形式賓語，構(gòu)成“主語 + 謂語 + it + 賓語不足語(名詞或形容詞) + to do sth”結(jié)構(gòu)，謂語動(dòng)詞常為find、think、feel等。
I found it difficult to stop him. 我發(fā)現(xiàn)攔截他很困難。
七、動(dòng)詞不定式可以作介詞的賓語。
Autumn harvest is about to start. 秋收即將開始。
I’m worrying about what to do next. 我正愁下一步該怎么辦。
八、作定語的動(dòng)詞不定式與被修飾詞有動(dòng)賓關(guān)系。
I have a lot of books to read. 我有許多書要讀。
此時(shí)，如果動(dòng)詞不定式動(dòng)詞為不及物動(dòng)詞，后面的介詞絕對(duì)不能省略。
We had only a cold room to live in. 我們只有寒室一間。
九、作定語的動(dòng)詞不定式與被修飾詞有主謂關(guān)系。
He is always the first to come and the last to leave. 他總是第一個(gè)到，最后一個(gè)走。
十、作定語的動(dòng)詞不定式與被修飾詞之間只有修飾關(guān)系。
We have no time to go to town today. 今天我們沒有時(shí)間去城里。
十一、作狀語的動(dòng)詞不定式常表示目的、原因、方向、結(jié)果等。
I’m glad to meet you. 見到你，我很高興。
They ran over to welcome the foreign guests. 他們跑過來歡迎外賓。
十二、不定式復(fù)合結(jié)構(gòu)“for sb to do sth”可用作主語、表語、定語、狀語等。
It’s for her to decide. 這得由她來決定。（表語）
There are many books for you to read. 這有許多書供你閱讀。（定語）
The book ids too difficult for children to read. 這本書太難了，孩子們看不懂。（結(jié)果狀語）
不定式復(fù)合結(jié)構(gòu)作主語時(shí)，需注意：
It’s + 形容詞 + for / of + sb + to do sth.
當(dāng)上面的形容詞指的是to do sth的性質(zhì)時(shí)，用介詞for。
It’s dangerous for children to swim in the river. 孩子在這條河里游泳很危險(xiǎn)。（游泳這件事情危險(xiǎn)）
當(dāng)上面的形容詞指的是sb的性質(zhì)時(shí)，用介詞of。這些形容詞往往修飾人：good, bad, polite, unkind, kind, nice, clever, right, wrong, careful, careless
It was careless of you to do that. 你這么做真粗心。（你這個(gè)人粗心）
十三、動(dòng)詞hear, see, feel, watch, notice, look at, listen to等后面的動(dòng)詞不定式作賓語補(bǔ)足語時(shí)不能帶to, 即常見的形式為: hear sb do sth等
Many people like to watch others play games. 許多人喜歡看別人玩游戲.
十四、let, make, have后面的動(dòng)詞不定式作賓語補(bǔ)足語, 也不能帶to; help后面的動(dòng)詞不定式作賓語補(bǔ)足語, to可有可無
She let us meet her at the station, but she didn’t come. 她讓我們?nèi)ボ囌居铀?卡她沒有來.
十五、十三和十四這兩種情況下的動(dòng)詞不定式在改被動(dòng)語態(tài)句子時(shí),必須將省略的to還原,也就是說,動(dòng)詞后需跟帶to的動(dòng)詞不定式.
We heard him sing every day.
He was heard to sing every day. 那時(shí)每天都聽到他唱歌.
十六、跟帶to的動(dòng)詞不定式作賓語補(bǔ)足語的動(dòng)詞還有: ask, beg, leave, like, love, hate, prefer, order, teach, tell, believe, find, know, want, think, understand, would like等
形式為: ask sb to do sth
Would you like me to visit him? 要不要我拜訪他?
I would prefer you not to come tomorrow. 我寧愿你明天不要來.
He ask the driver to stop the motobike. 他要那位司機(jī)攔下那輛摩托車.
十七、區(qū)別下列詞組的不同含義:
①like to do sth
like doing sth
②stop to do sth
stop doing sth
③remember to do sth
remember doing sth
④forget to do sth
forget doing sth
十八、It takes sb some time to do sth.花費(fèi)某人一段時(shí)間干某事.
It took me half an hour to do my homework yesterday.昨天我花了半小時(shí)做回家作業(yè).
It took Jim an hour and a half to read the book.吉姆花了一個(gè)半小時(shí)看這本書.
It took mother one and a half hours to do the housework.母親花了一個(gè)半小時(shí)干家務(wù).
用漢字表述上面的句型為:It + take + 人 + 一段時(shí)間 + to do sth.
一段時(shí)間形式往往為像這樣的例子:fifteen minutes15分鐘,an hour一個(gè)小時(shí), two days兩天, half a month半個(gè)月,a year and a half一年半...等等
十九、不定式的特殊句型too…to…
①too…to 太…以至于…
He is too excited to speak.
他太激動(dòng)了，說不出話來。
---- Can I help you ? 需要我?guī)兔?
---- Well, I'm afraid the box is too heavy for you to carry it, but thank you all the same.不用了。這箱子太重，恐怕你搬不動(dòng)。謝謝您。
②如在too前有否定詞，則整個(gè)句子用否定詞表達(dá)肯定， too 后那個(gè)詞表達(dá)一種委婉含義，意 為"不太"。
It's never too late to mend.(諺語)
改過不嫌晚。
③當(dāng)too 前面有only, all, but時(shí)，意思是：非常… 等于very。
I'm only too pleased to be able to help you. 我非常高興能幫助你。
He was but too eager to get home. 他非常想回家。
二十、不定式的特殊句型Why not
"Why not +動(dòng)詞原形"表達(dá)向某人提出建議，翻譯為："為什么不……?" "干嗎不……?"
例如：
Why not take a holiday?
干嗎不去度假?
練習(xí)
根據(jù)括號(hào)內(nèi)的動(dòng)詞,用適當(dāng)?shù)男问教羁?空內(nèi)可能不只填一個(gè)詞,使句子完整意思正確
1. They usually __________ kites on Sundays. (fly)
2. Look! The dogs __________ after the cat. (run)
3. Miss Gao __________ English in our school since she came here. (teach)
4. The class meeting _________ last Wednesday afternoon. (hold)
5. You should let him __________ the work by himself. (finish)
6. Meimei __________ to wash the old woman’s clothes twice every week. (go)
7. Mr Jiang __________ us Chinese last term. (teach)
8. My father __________ back from Japan tomorrow. (come)
9. It’s seven o’clock now. The Greens __________ breakfast together. (have)
10. Jim __________ many Chinese songs since he came to China. (learn)
11. Please remember __________ the window when you leave the room. (close)
12. After school some students began to do some __________ in the classroom. (clean)
13. English __________ widely in the whole world today. (speak)
答案
1. fly, 2. are running, 3. has taught, 4. was held, 5. finish, 6. goes / went,
7. taught, 8. is going to come / is coming / will come / comes 9. are having,
10. has learned, 11. to close, 12. cleaning,
13. is spoken