动词不定式动词不定式是一种非限定动词,有不定式符号to加动词原形构成.有时不带to,动词不定式具有名词、形容词、和副词的特征,同时保留有动词的特征.它无人称和数的变化.在句中不作谓语.基本形式：to+动词原形作主语.(谓语动词用单数形式,常用it作形式主语,而不定式作为真正的主语放在谓语后面)To play football in the street is dangerous. → It is dangerous to play football in the street. To get up early is good for our health. → It’s good for our health to get up early.It is/was +adj + (for sb.)+ to do sth. 当形容词为easy important interesting dangerous hard difficult impossible necessary safe pity 等表客观的情况的形容词,后接for sb.It’s important for us to study well.It’s easy for me to play basketball.It’s difficult for us to finish it in two hours.It is/was + adj + (of sb.) + to do sth. 当形容词为 nice good right wrong kind foolish clever wise careful polite careful 等表主观的感情或态度的形容词,后接of sb.来表这个人具有的某中品质或性格.It was clever of them to avoid a terrible accident.→ They was clever to avoid a terrible accident.It kind of you to help me. →You are kind to help me.It’s very foolish of you to make the same mistake. → You are very foolish to make the same mistake.作表语(说明主语所表达的内容)My job is to feed animals./His dream is to be a scientist.His wish is to be a college student./ I think the best way to raise money is to sell flowers.作宾语s+v. + to do sth. / S + V + not to do sth.常用的词有want, like, hope, wish, start, bigin, forget, remember, decide, need, try, learn, plan, love, agree, fail, choose等动词. I forget to close the door./ He wanted to buy some books.I hope to see you again. /They decided to visit the Great Wall.be + adj + to. (形容词有pleased, glad, sorry, afraid, sure, ready,willing等)To 用在表感情的形容词的后面,不定式用来说明产生这种感情的原因.I am sorry to trouble you./ I am pleased to see you.He is afraid to walk alone at night./ I am sure to win. 作宾语补足语带to 的宾语补足语结构：S + V. + 宾语 +to do sth. /S + V. + 宾语 + not to do sth. 这类词有tell, ask, order, wish, teach, want, would like, like, know, allow, get, invite等, help sb. to do/do sthHe often asks me to help him with his English.He often teaches me to play the violin.His father wanted him to buy some fruit.He asked me not to open the door.Kangkang always allows his friends to borrow his bike. 不带to的宾语补足语.即是动词原形作宾语补足语.结构: S + V + 宾语+ 动词原形(省略to) 这类动词有feel, listen to, hear, make, let, have, notice, watch, see, look at等词.He often make me laugh. (laugh =to laugh)His father don’t let him swim in the river. (swim =to swim)I often see him play football after school.(play = to play)I heard him sing in the next room. (sing = to sing)在被动语态时,to要加回去.I am often made to laugh by him.He isn’t let to swim in the river by his father.He is often seen to play football after school by me.He was heard to sing in the next room by me.作状语表示目的(相当于in order to, so as to)He got up early to catch the train. (to catch the train = in order to/so as to catch the train)Maria came here to borrow my bike. (to borrow my bike = in order to / so as to borrow my bike)He went abroad to study. (to study = in order to / so as to study)表示结果.常用too --- to 太--- 而不能, enough --- to—足够 --- 能, so --- as to 如此--- 以致.She was too young to carry the box.He was so careless as to make a lot of mistakes.He was too excited to say a words. I have enough money to buy the car.表示原因.(也可看作宾语) I’m soory to hear that./We was surprised to find him there.We are ploud to be young people of China./I am pleased to see you.作定语后置定语The best time to go there. The best way to raise money. The answer to the question. The way to the station动宾关系.(动词不定式与被修饰的人或物构成的) I have lots of homework to do.(to do 与homework是动宾关系)I have words to say. (to say 与 words 是动宾关系)She has many books to read. (to read 与 books是动宾关系)He has no food to eat. (to eat food)当不定式中的动词是不及物动词时,其后的介词不能省略.You have nothing to worry about. /I need a pen to write with. We have some tapes to listen to./The baby isn’t easy to look after./ I want to rent a three-bedroom house to live in.主谓关系He is the first one to get there. (the first one 与 to get there 是主谓关系)Can you find a person to help me. (a person 与to help me 是主谓关系)He need someome to go and find a doctor. (someone 与to go and find a doctor 构成主谓关系)不具主谓或动宾关系It’s time to have lunch./It’s her turn to read the dialogue.There is no need to help me.七．不定式前加疑问词what, how, when, who, where等疑问词.1. 作主语.When to start is unknow to us. 什么时候开始我们不知道.How to search the Internet is very important. 怎样上网非常重要.2. 作表语.The question is what to do next. 问题是下一步做什么.3. 作宾语.I didn’t decide which one to buy. 我没有决定要买哪一个.Could you tell me how to get to the hospital? 你能告诉我怎样到达医院吗?He doesn’t know whom to ask. 他不知道去问谁.疑问词 + 不定式 结构可以转换为从句,从句中的主语要与主句的人称保持一致.Can you tell me how to search the Internet? = Can you tell me how I can / will/ should search the Internet?She doesn’t know where to go. = She doesn’t know where she will / can / should / go. I don’t know what to do. = I don’t know what I can / will/ should / do.