动词不定式是由“不定式符号to 动词原形”构成的一种非谓语动词结构。有些动词不定式不带to，动词不定式可以作句子的主语、表语、宾语、定语、补语、状语或单独使用。不定式保留动词的某些特性，可以有自己的宾语、状语等。动词不定式和它后面的宾语、状语等一起构成短语，叫作不定式短语。现对九年级动词不定式的用法作一次简要梳理。

一、用作主语

直接把动词不定式置于句首的情况不多，多数情况用it作形式主语，把真正的主语——动词不定式置于句末，特别是不定式短语较长时。动词不定式作主语，谓语动词用第三人称单数形式。带疑问词的不定式短语作主语常置于句首，复合不定式结构作主语常置于句末。如：

1.As young adults, it is our duty to try our best to deal with each challenge... (p.8)

2.The head teacher said it was necessary to talk with his mother. (p.16)

3.How to make requests politely is important.(p.93)

二、用作表语

动词不定式作表语，常说明主语的内容、性质、特征。如：

1.The best way to improve your English is to join an English club. (p.7)

2.The first thing is to greet the teacher. (p.96)

三、用作宾语

1.可以接带to的动词不定式作宾语的动词主要有：要求选择同意(ask, choose, agree)，期望决定学习(expect, hope, decide, learn)，宁可假装知道(prefer, pretend, know)，希望想要愿意(wish, want, would like / love)。如：

1)We decided to talk to some students about why they go there. (p.88)

2)He prefers to eat white bread and rice.(p.50)

3)Id love to visit Mexico.(p.53)

2.动词decide, know, learn, show, teach, tell...，介词结构on...可用疑问词带to的不定式短语作宾语，但why后面的不定式不带to。如：

1)Could you please tell me where to park my car?(p.92)

2)It gives advice on what to do in lots of different situations. (p.32)

3.动词feel, find, make, think等后面，可以用it作形式宾语代替真正的宾语——动词不定式，句子结构是...feel / find / make / ... it adj. / n. to do...。如：

I find it difficult to remember everything. (p.98)

4.既可接动词不定式又可接ving形式作宾语，意思差别不太大的动词有begin, start, like, love等。一般说来，动词不定式表一次、数次的具体动作、将来动作或动作的全过程，ving形式表习惯性的连续动作。但是这种区别并不很严格，特别是美国英语，即使是习惯性的动作也可以用动词不定式。如：

1)Then I started to watch English-language TV.(p.6)

2)I’m beginning to understand my Chinese roots, and who I am. (p.116)

begin用了进行时态，后面只接不定式作宾语，表示事情刚开始，还要继续下去。

3)I like to eat vegetables. (p.118)

感知动词like, love, know等一般不用进行时态。

5.后接动词不定式或ving形式作宾语，意思差别较大的动词有forget, remember等。后接不定式作宾语，表动作尚未发生;后接ving形式作宾语，表动作已经发生。stop to do停下来做另外一件事，to do是目的状语;stop doing停止做、不做当前这件事，doing是宾语。try to do尽力做，try doing试试看;go on to do接着做另外的事，go on doing继续做原来的事。如：

1)When I left home, I had forgotten to bring it with me.(p.107)

2)I stopped using them last year. (p.121)

四、用作定语

1.句子的主语或宾语是动词不定式的逻辑主语，不定式与其所修饰的名词、代词等存在逻辑的动宾关系时，用动词不定式的主动式。如：

1)I have so many chores to do today.(p.112)

2)I cant think of any good advice to give her. (p.31)

3)Basketball has also become a more popular sport for people to watch.(p.75)

2.动词不定式所修饰的名词是place, time, way等时，不定式与这些名词呈现出动状关系或同位关系。如：1)He needs time to do homework.(p.19)

2)Is that a good place to hang out?(p.88)

3)You want to know the best way to get around the city.(p.127)

3.在“there be...”句型里，句子的主语是动词不定式动作的对象，常用主动式。如：

1)There’s just so much to see and do here.(p.49)

2)... but there are still many things to do there.(p.54)

五、用作补语

动词不定式作补语时，在主动语态句里补宾语，在被动语态句里补主语，句子的宾语或主语是不定式动作的逻辑执行者。如果不定式是to be done，句子的宾语或主语就是逻辑承受者。

1.在主、被动语态句里用带to的动词不定式作补语的动词主要有：要求允许提议(ask, allow, permit, advise)，期望邀请鼓励(expect, suppose, invite, encourage)，教导告诉想要(teach, tell, want)，等待希望愿意(wait for, wish, would like / love)。如：

1)Id invite her to have dinner at my house.(p.29)

2)Teenagers should be allowed to choose their own clothes. (p.18)

3)Email English is supposed to be used on mobile phones.(p.101)

2.动词不定式作补语，在主动语态句里不带to，被动语态句里带to时多数动词是感官动词和使役动词，包括四“看”：look at, observe, see, watch，三“让”：have, let, make，二“听”：hear, listen to，一“感觉”：feel，一“注意”：notice。如：

1)This picture makes me feel tense!(p.106)

2)Of course we want to see Liu Yu achieve his dreams.(p.24)

3.help后接动词不定式作补语，to可带可不带。一般说来，带to表间接帮助，不带to表直接帮助。在被动语态句里，或者用不定式的否定式作补语时要带to。如：

1)... they can help you to compare two different products so that you can buy the one you really need.(p.106)

2)Using email English helps you write quickly. (p.100)

4.be said, be sure, happen, seem等后面可以接带to的动词不定式作主语的补语。如：

1)He doesn’t seem to have many friends.(p.19)

2)Be sure not to miss them if they come to a city near you.(p.114)

六、用作状语

1.目的状语，置于句首或句末，置于句首时常表示强调。如：

1)In order not to offend people, learning about language etiquette is just as important as learning grammar or vocabulary.(p.93)

2)A group of young people got together to(in order to / so as to) discuss this question. (p.50)

to do / in order to do / so as to do用作目的状语，置句末时都可以用，置句首时只用to do / in order to do。so as to do一般不置于句首，可以引导结果状语从句，in order to do不引导结果状语从句。

2.原因状语，多见于“sb. be adj. to do...”结构句中。如：

1)My dogs name is “Lucky”—a good name for him because I feel very lucky to have him.(p.66)

2)On Monday he told a radio interviewer that he had run out of money to buy old bikes. (p.64)

3.结果状语，多见于“too...to”，“enough to...”结构句中。如：

1)Then I’m too tired to do well. What should I do?(p.28)

2)The room needs to be big enough for three people to live in.(p.56)

4.有些动词不定式作状语，常说明前面形容词的性质和特性。动词不定式与句子的主语有逻辑的动宾关系。动词不定式前面的形容词一般是：cheap, dangerous, difficult, easy, fun, hard, interesting, necessary。不定式常用主动式表被动意义。

... the mistakes you made are necessary for you to learn and understand.(p.116)

这类句子中的动词不定式可改为主语。

5.独立动词不定式多用作插入语，表示说话人的心理状态或对事情的看法。如：

1)Id like to stay healthy, but to be honest, I only eat food that tastes good.(p.50)

2)To begin with, she spoke too quickly, and I couldn’t understand every word. (p.6)

七、动词不定式的复合结构

动词不定式的复合结构是“for / of sb. to do sth.”，for / of引出不定式动作的逻辑主语。这种结构在句子中可以作主语、宾语、表语、定语、状语等。不定式复合结构的介词用for还是of，主要决定于前面形容词的性质。一般说来，of前面的形容词是careful, clever, foolish, good, kind, nice, wise等，既说明人的特性，又说明不定式动作的特性。for前面的形容词是dangerous, difficult, easy, hard, heavy, important, interesting, necessary等，一般说明不定式动作的特性，不说明人的特性。前面如果是名词用for。如：

1.Its also probably a good idea for parents to allow teenagers to study in groups during the evening. (p.22)

2.Zoos are terrible places for animals to live.(p.120)

八、带疑问词的不定式短语

动词不定式前面可以带疑问代词what, which, who或疑问副词how, when, where, why等。这种结构起名词的作用，在句子里用作宾语、主语、表语等，或者单独使用。要注意的是，why后面的不定式不带to。如：

1.用作句子的成分。

1)I don’t know what to try next. (p.49)(作宾语)

2)Where to go is not decided yet.(作主语)

2.单独使用时相当于一个特殊疑问句。

1)What to do next?(=What will we / you do next?)

2)Why go there?(=Why do we / you go there?)

九、动词不定式的否定式

不定式的否定式是not / never to do...，不带to的不定式的否定式是not / never do...如：

1.Sometimes they have disagreements, and decide not to talk to each other.(p.8)

2.His parents tell him never to drive after drinking.