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动词不定式 概述：
不定式的构成非常简单：to do sth (do 代表动词原形)，其否定
形式是not to do sth，有时也可以不带to。动词不定式没有人称和数的变化， 具有名词、形容词和副词等的功能，可以担当除谓语外的任何句子成分，即：主语、宾语、表语、定语、状语、补足语、同位语。
1.I’d like to help homeless.(to help homeless 作would like 的 宾语） 2.You could ask hospital to let you visit the kids and cheer them up.（不定式to let you visit the kids and cheer them up做ask的宾语。） (一）.结构：to +动词原形 （二）否定形式：not+不定式
（三）动词不定式的形式是“to+动词原形”，但to 有时要省略，动词不定式在具体运用时，用不用to,取决于它所跟的谓语动词的用法。 1.带to的不定式结构 （1）带
to 的不定式结构的谓语动词有：
want;ask;tell;hope;learn;try;decide;forget;remember;like;love;stop等 Eg.I want to play basketball.
（2）动词不定式可以和疑问词what;which;how;where等连用。
Eg. I don’t know how to do it. 2.不带to的不定式结构
（1）在感官动词后：如：see,hear,watch,feel,notice等。 Eg; I saw the teacher get out.
（2）在使役动词后：let,make,have等 Eg.let us play basketball. (3)在why not 后省略不定式to Eg.why not go with us?
四．动词不定式在句子中的成分。 （1）不定式作主语： 一般位于句首，谓语用单数
To go to college is our ideal. 上大学是我们的理想。 To learn foreign languages is difficult. 学外语很难。 为了平衡句子，通常用it做形式主语替不定式，即：
It’s+名词/形容词+for/of sb.+to do sth. (注：此句式中不定式逻辑上的主语可由for或of引出，当表语的形容词为修饰逻辑主语sb. 的kind，nice，good，polite，clever，foolish，right，wrong等时，逻辑主语由of引出)
则上面两句话可变为： It’s our ideal to go to college.
It’s difficult (for us) to learn foreign languages. 又如：It’s kind of you to say so. 你那样说真好。
(2)不定式作宾语：
I like to watch TV. 我喜欢看电视。 He wants to swim. 他想要游泳。 (3)不定式作表语：
常用在系动词be, seem, get, remain等后作表语，如：
The meaning of the word is to go quickly. 这个词的意思是快点走。 To the doctor, the most important thing is to save the lives. 对于医生来说，最重要的是治病救人。
This suit doesn’t seem to fit her. 这套衣服似乎不合她身。 (4)不定式作定语
通常放在其修饰的名词或代词之后。
He has something important to do. 他有重要事情要做。 (5)不定式做宾语补足语：
（1）做动词ask,like,tell等的宾语补足语时，动词不定式to不可省略。 Eg:he asked me to clean up the city partk.
(2)做使役动词make,let,have等及感官动词hear,see,watch,feel等宾语补足语时，要省略不定式to
Eg:the teacher let him do the homework.
(3)做动词help 的宾语补足语，不定式to 可带可不带。 Eg；could you help me(to)carry the bag? （五）不定式做状语
（1）放在句首或句尾做目的状语。
Eg.he went to the shop to buy some pencils. (2).跟在形容词或过去分词后状语 Eg.i’m glad to see you. I’m sorry to hear that. (3)用在too....to...的结构中 Eg.she is too yong to get dressed. 不定式练习题
1.I advised _________ at once.
A.him to starting B.him to start C.to starting D.to start
2.You shouldn’t allow ________ games near the classroom, for it’s too noisy.
A.student playing B.to play C.students to play D.to playing 3.Don’t forget ________ the letter for me on your way home. A.post B.to post C.posting D.posted
4.Have you forgotten ________a ruler from Betty? Please remember ________it to her tomorrow.
A.borrowing, to return B.borrowing, returning C.to borrow, to return D.to borrow, returning
5.I forget _______ them _______ in the school garden.
A.allowing, playing B.allow, to play C.allowing, to play D.to allow, playing
6.He finished his homework and then went on _________ me.