動(dòng)詞不定式作賓語且過長時(shí)常請(qǐng)it作形式賓語，而讓真正的賓語不定式斷后。例如

　　The man downstairs found it hard to fall asleep.

　　2. 小品詞to 的回避與復(fù)出

　　許多動(dòng)詞如teach，ask （要；讓），tell，beg 等后常有帶to的動(dòng)詞不定式作賓補(bǔ)；但let，have，make （讓；使），feel，hear 等后作賓補(bǔ)的不定式結(jié)構(gòu)，to 要回避。但在被動(dòng)語態(tài)里to須“重出江湖”；help 后作賓補(bǔ)的不定式可加to，也可省略to.例如

　　The policeman made the young woman move her car.

　　The young woman was made to move her car by the policeman.

　　[提示] 對(duì)不定式進(jìn)行否定可在其前加not.如：let sb not do sth； tell sb not to do sth. 把直接引語為祈使句的句子變?yōu)殚g接引語，直接引語一般轉(zhuǎn)換成不定式作賓補(bǔ)。例如

　　The policeman said. “Don’t play football in the street，children！”

　　The policeman asked the children not to play football in the street.

　　3. 回答原因，作目的狀語

　　不定式（短語）常跟在come， go， run， hurry 等動(dòng)詞后作目的狀語；或以“in order to +動(dòng)詞原形”、“so as to +動(dòng)詞原形”等形式出現(xiàn)，或回答what . . . for？ / why . . . ？問句。例如

　　-Hi， Peter！ Why are you in such a hurry？

　　-To catch the 7：30 train.

　　[提示] 有時(shí)目的狀語可置于句首，意為“為了……”，相當(dāng)于in order to.例如

　　To catch the bus， you must get up early.

　　在stop后的動(dòng)詞不定式其實(shí)是作目的狀語，意為“停下來做另一件事”。例如

　　Let’s stop to have a meal. I know a good restaurant near here.

　　4. 作狀語，簡化相應(yīng)的復(fù)合句

　　作結(jié)果狀語的不定式常以“enough to . . . ，only to . . . ， too . . . to . . . ”等形式出場，并能簡化成so . . . that . . . 句式。例如

　　Liu Mei was so lucky that she received many books from Project Hope.

　　Liu Mei was lucky enough to receive many books from Project Hope.

　　5. 作后置定語

　　作定語時(shí)，不定式（短語）常置于被修飾的名詞、不定代詞等之后。例如

　　Now China is the third country to send its astronauts into space after Russia and the US.

　　[提示]如果不定式（短語）是不及物動(dòng)詞，其后應(yīng)有必要的介詞/副詞。例如

　　I found a nice place for him to live in.

　　6. 不定式be to do sth可表將來

　　be to do sth 表將來，意為“將要做某事”。例如

　　Our train is to leave at eight.

　　7. 時(shí)代弄潮兒“疑問詞+不定式”

　　“疑問詞+不定式”結(jié)構(gòu)中的疑問詞包括疑問代詞which， who （m）， what 和疑問副詞how， when， where 等，并常簡化相應(yīng)的從句，但當(dāng)主句與從句的主語不一致時(shí)，不定式常用被動(dòng)形式。例如

　　The little girl wanted to know when her father could take her to Pairs.

　　The little girl wanted to know when to be taken to Pairs by her father.