（1）作主語(yǔ)：To finish the work in ten minutes is very hard.十分鐘之內(nèi)完成這項(xiàng)工作是很難的.To lose your heart means failure.灰心意味著失敗.動(dòng)詞不定式短語(yǔ)作主語(yǔ)時(shí),常用it作形式主語(yǔ),真正的主語(yǔ)不定式置于句后,例如上面兩句可用如下形式：It is very hard to finish the work in ten minutes.十分鐘之內(nèi)完成這項(xiàng)工作是很難的.It means failure to lose your heart.灰心意味著失敗.常用句式有：1、It+be+名詞+to do.2、It takes sb.+some time+to do.3、It+be+形容詞+of sb +to do.常用careless,clever,good,foolish,honest,kind,lazy,nice,right,silly,stupid,wise,等表示贊揚(yáng)或批評(píng)的形容詞,不定式前的sb.可作其邏輯主語(yǔ).（2）作表語(yǔ)：Her job is to clean the hall.她的工作是打掃大廳.He appears to have caught a cold.他似乎感冒了.（3）作賓語(yǔ)：常與不定式做賓語(yǔ)連用的動(dòng)詞有：want,hope,wish,offer,fail,plan,learn,pretend,refuse,manage,help,agree,promise,prefer,如果不定式（賓語(yǔ)）后面有賓語(yǔ)補(bǔ)足語(yǔ),則用it作形式賓語(yǔ),真正的賓語(yǔ)（不定式）后置,放在賓語(yǔ)補(bǔ)足語(yǔ)后面,例如：Marx found it important to study the situation in Russia.馬克思發(fā)現(xiàn)研究俄國(guó)的情況是很重要的.動(dòng)詞不定式也可充當(dāng)介詞賓語(yǔ),如：I have no choice but to stay here.我只能留在這里,別無(wú)選擇.He did nothing last Sunday but repair his bike.他上周日除了修他的自行車什么也沒(méi)干.動(dòng)詞不定式前有時(shí)可與疑問(wèn)詞連用,如：He gave us some advice on how to learn English.他給了我們一些學(xué)英語(yǔ)的建議.（4）作賓語(yǔ)補(bǔ)足語(yǔ)：在復(fù)合賓語(yǔ)中,動(dòng)詞不定式可充當(dāng)賓語(yǔ)補(bǔ)足語(yǔ),如下動(dòng)詞常跟這種復(fù)合賓語(yǔ)：want,wish,ask,tell,order,beg,permit,help,advise,persuade,allow,prepare,cause,force,call on,wait for,invite.此外,介詞有時(shí)也與這種復(fù)合賓語(yǔ)連用,如：With a lot of work to do,he didn't go to the cinema． 他有很多工作要做,所以沒(méi)去電影院.有些動(dòng)詞如make,let,see,watch,hear,feel,have等與不帶有to的不定式連用,但改為被動(dòng)語(yǔ)態(tài)時(shí),不定式要加to,如：I saw him cross the road.我看見他橫過(guò)公路.He was seen to cross the road.他被我看見橫過(guò)公路.（5）作定語(yǔ)：動(dòng)詞不定式作定語(yǔ),放在所修飾的名詞或代詞后.與所修飾名詞有如下關(guān)系：①動(dòng)賓關(guān)系：I have a meeting to attend.我有一個(gè)會(huì)議要出席.注意：不定式為不及物動(dòng)詞時(shí),所修飾的名詞如果是地點(diǎn)、工具等,應(yīng)有必要的介詞,如：He found a good house to live in.他找到了一個(gè)居住的好房子.The child has nothing to worry about.這個(gè)孩子無(wú)憂無(wú)慮.What did you open it with?你用什么打開它?如果不定式修飾time,place,way,可以省略介詞：He has no place to live.他無(wú)處安身.This is the best way to work out this problem.這是解決這個(gè)問(wèn)題的最好辦法.如果不定式所修飾名詞是不定式動(dòng)作承受者,不定式可用主動(dòng)式也可用被動(dòng)式：Have you got anything to send?你要送什么東西嗎?Have you got anything to be sent?你有什么東西需要送嗎?②說(shuō)明所修飾名詞的內(nèi)容：We have made a plan to finish the work.我們制定了一個(gè)完成工作的計(jì)劃.③被修飾名詞是不定式邏輯主語(yǔ)：He is the first to get here.他第一個(gè)來(lái)到這兒.（6）作狀語(yǔ)：①表目的：He worked day and night to get the money.他夜以繼日地工作來(lái)賺錢.She sold her hair to buy the watch chain.她賣掉了自己的頭發(fā)來(lái)買那條表鏈.注意不定式放句首時(shí),邏輯主語(yǔ)與句子主語(yǔ)要一致：wrong：To save money,every means has been tried.right：To save money,he has tried every means.為了省錢,他使出了渾身解數(shù).wrong：To learn English well,a dictionary is needed.right：To learn English well,he needs a dictionary.為了學(xué)好英語(yǔ),他需要一本詞典.②表結(jié)果(往往是與預(yù)期愿望相反的結(jié)果 意料之外)：常放在never only后 He arrived late only to find the train had gone.他來(lái)晚了,只見火車已經(jīng)走了.I visited him only to find him out.我去拜訪他,只見他出去了.③表原因：常放在形容詞后面 They were very sad to hear the news.他們聽到這條新聞非常傷心.④表程度：It's too dark for us to see anything.太暗了,我們什么也看不見.The question is simple for him to answer.這問(wèn)題由他來(lái)回答是很簡(jiǎn)單的.（7）作目的狀語(yǔ)：既可以放在句首,也可以放在句尾 To tell you the truth,I don't like the way he talked.說(shuō)實(shí)話,我不喜歡他講話的方式.（8）不定式的省略：保留to省略do動(dòng)詞.If you don't want to do it,you don't need to.如果你不想做這件事,你就不必做.（9）不定式的并列：第二個(gè)不定式可省略to.He wished to study medicine and become a doctor.他希望學(xué)醫(yī)并成為醫(yī)生.