动词不定式讲解一动词不定式：to + 动词原形1.基本用法：可在句中作主、宾、表、定、状、补。
1）作主语To get up early is a good habit.It's so nice to hear your voice.(it 为形式主语)It is important for us to learn English well.It’s silly of you to do such a thing.How to improve our English is still a problem.2) 作宾语We all hope to see you.They found it hard to learn Chinese. （it 为形式宾语）I do not know what to do next. （疑问词+ 不定式）He asked me how to improve English.（疑问词 +不定式）3）作表语①一般情况My work is to clean the room every day.His dream is to be a doctor.The question is how to put it into practice. 问题是怎样把它付诸实施。
He seemed to have known the news.②如果主语是不定式，则表语也用不定式。
例如：To see is to believe.Seeing is believing.③作表语的不定式有时可省略符号to：这时主语部分必须含有动词do,而作表语的不定式则解释do 的精确意思。
All I did was (to) give him a little help.What we want to do now is (to) have a rest.4)作定语①不定式作定语时，被修饰的名词常为它的逻辑宾语。
不定式与该名词存在逻辑上的动宾关系。
I have some clothes to wash.（后置定语）He has something important to tell you.如果不定式是不及物动词，后面应有必要的介词。
Give me a pen to write with.I need a warm room to live in.②逻辑上的主谓关系。
He was the first teacher to come.I need a box to hold my books.Is there anyone to answer my question?He was the last student to have left the classroom .( 不定式完成式)③逻辑上的同位关系。
Everyone has the right to speak at the meeting= Everyone has the right that he may/ can speak at the meeting.Do keep your promise to write to me.= Do keep your promise that you will write to me.5)作状语①作目的状语He will go to the station to meet his friend.I often read China Daily in order to (或so as to ) improve my English.（in order to可放在句首； so as to 只能放在句中）。
I come here only to say good-bye to you.②作结果状语I hurried to his house only to find he was out.He is (not) old enough to join the army.It’s too late to play basketball.He was so angry as to be unable to speak.③作原因状语I was surprised to see him here.They were pleased to hear the good news.I am glad to meet you .④在形容词后作状语This question is easy to answer.6）作补语He wants his son to become a lawyer.She encouraged me to try again.They persuaded him to give up smoking.They believe him to be writing a new book .他们认为他正在写一本新书。
He wanted the letter to be typed at once .The letter was wanted to be typed at once.(主补)注：有些动词后跟不带to 的不定式作宾语补足语。
常见的有：①感官动词feel, hear ,see, watch, notice , observe②使役动词let, make, have③ help ：help sb. do…… 或help sb. to do…… 两种说法均可。
I often hear him sing this song.The boss made the workers work 12 hours a day.当此类句子改为被动语态时，要补上to.He is often heard to sing this song.The workers were made to work 12 hours a day.☆在 think, find, consider, discover等动词后常用to be +adj.结构作宾补，有时to be 可省略。
We all think/ consider/ find/ discover him (to be) kind and honest. 我们都认为/发现他既善良又诚实。
2.不定式的时态/方式1) 一般式：有时与谓语动词表示的动作同时发生，有时发生在谓语动词的动作之后。
（to do ）He seems to know this.I hope to see you again. = I hope that I'll see you again.我希望再见到你。
2) 进行式：表示动作正在进行，与谓语动词表示的动作同时发生。
(to be doing )He seems to be eating something.3) 完成式：表示的动作发生在谓语动词表示的动作之前。
(to have done)I'm sorry to have given you so much trouble.He seems to have caught a cold.4) 完成进行式： (to have been doing)She is known to have been working on the problem for many years.He pretended to have been studying.3. 动词不定式的否定式：not to doTell him not to shut the window.She pretended not to see me when I passed by.例1）Tell him ___ the window.A. to shut notB. not to shutC. to not shutD. not shut答案：B。
tell sb. to do sth 的否定形式为tell sb. not to do sth..例2) She pretended ___ me when I passed by.A.not to seeB. not seeingC. to not seeD.having not seen答案：A。
pretend 后应接不定式。
其否定形式为pretend not to do sth.。
例3）Mrs. Smith warned her daughter ___ after drinking.A. never to driveB. to never driverC. never drivingD. never drive答案：A。
warn sb. to do sth. 的否定形式为warn sb.not to do sth. 此处用的是否定词never.例4) The boy wanted to ride his bicycle in the street，but his mother told him ____.A. not toB. not to doC. not do itD. do not to答案：A。
not to 为not to do it 的省略形式。
例5) The patient was warned ___ oily food after the operation.A. to eat noB. eating notC. not to eatD. not eating答案：C。
此处为warn sb. to do 的被动否定形式，即be warned not to do。
4.动词不定式的省略1）不定式在使役动词 let, have, make和感官动词 see, watch, notice , observe, hear, smell, feel, find 等后作宾补时，省略to。
help 可带to，也可不带to→help sb (to) do sth。
2) Why not 后面接不带to 的不定式。
常用来表建议。
Why not have a break?3）but和except：but/except前的部分出现实义动词do时，其后面出现的动词不定式可以不带to。
He wants to believe anything but to take the medicine.比较：but前有实义动词do时，but后的不定式需要省去to. 如：Last night I did nothing but (to )watch TV.He does everything except (to) work.4) 由and, or或than连接的两个不定式，第二个不定式的to 可以省去。