动词不定式在英语中的使用频率很高，可以作主语、表语、宾语、同位语、补语及独立成分等。带to的不定式是经常见到的，但有时也会遇到省略to的不定式。那么，什么时候可以省略to，什么时候又必须保留呢？这是大家学习不定式时的难点，下面笔者就常见的不定式的几种用法进行一下简单总结。

　　一、不带to的不定式常见于以下几种情况：

　　1.如果主语是all或是what引导的从句，主语受first, only, one, least或形容词最高级修饰,且后面的从句或短语中有实意动词do时，作表语的不定式前不用to。如:

　　The only thing I can do was keep silent.

　　What he wants to do is complete the whole task as soon as possible.

　　All he does is study hard.

　　all作主语时，如果从句含有say，其后作表语的动词不定式有时可以省略to。如：

　　All they say is hurry up.

　　但在其他情况下，to不能省略。如：

　　All I wanted was to help him.

　　2.在一些固定搭配中，如：let go，make believe，go hang等，不用to。如：

　　We'll have to make do with dry bread.

　　He made believe he was innocent.

　　They can't let things go hang.

　　3.在would rather，would sooner(宁愿……也不)，might (just) as well，cannot help but，cannot but (不得不)，do nothing besides，do nothing but，do nothing than，had better，had best等结构后，用不带to的不定式。

　　The soldiers would rather die than surrender.

　　I cannot but decline his offer.

　　He did nothing else than cry.

　　4. rather than，sooner than (宁愿……也不)位于句首时，其后的动词不用to。

　　Sooner than run the risk of losing everything，they agreed to the terms.

　　当rather than，sooner than位于其它位置时，其后的不定式可带to，也可不带to。如：

　　He prefers to rent a car rather than to have one of his own.

　　Mary decided to write rather than telephone.

　　5.在feel, hear, listen to, see, look at, watch, observe, perceive, let, make, have等动词后，动词不定式作宾语补足语时不用to。如：

　　I have heard both teachers and students speak well of him.

　　He made me give up the exam.

　　6.为避免重复,不定式可省去to。如：

　　He was at a loss as to what to think and say. (say前省略to)

　　It is just impossible to see that and not feel angry.(feel前省略to)

　　但是如果两个不定式表示对照或对比，则不可省略to。如：

　　To die or not to die-that is the question.

　　They came not to save us, but to conquer us.

　　7.在介词except, than, besides, save, but之后，如果这些词前有动词do，则常用不带to的不定式。如：

　　What do you like to do besides swim?

　　She can do everything except cook.

　　We have nothing to do save send for the doctor.

　　但当动词不是do时，to不能省略。如：

　　The doctor told him nothing but to stop smoking.

　　8. why+不带to的动词不定式，引导疑问句，表明做某事是愚蠢的或无意义的，含有不满或批评的语气。

　　Why leave the door open?

　　why not+不带to的动词不定式，可用来提出建议或劝告。

　　Why not take a holiday?

　　Why not answer my question?

　　9.两个动词不定式由and, or, except, but或than连接在一起时，第二个动词不定式常常不带to。如：

　　Do you want to have lunch now or wait till later?

　　I intend to call on him and discuss this question again.

　　但几个动词不定式连用，并表示对比或强调时，to不能省略。如：

　　The student must learn to read extensively, to analyze what he reads and to summarize the main points presented.

　　I haven't decided to go home or to stay at school this summer vacation.

　　在不用连词的情况下，第二个to也要保留。如：

　　He likes to stay with the peasants, to work in the fields with them.

　　10.在某些形容词后，to可省略，尤其是在从句中，这种现象更多。如：

　　One can't be forced if he's not ready (to).

　　11.某些名词后的to可以省略。如：

　　He will never leave you；he has not the courage (to).

　　12.在某些动词之后，可省略to。如：

　　Can you help me to persuade my mother?

　　OK, I'll try (to).

　　13.在go, come和run后可省略to，直接用另一个动词，多用在表示命令、建议、请求或意愿的句子中。如：

　　Come have a drink with us.

　　Let's go hear a concert.

　　I'll go see my sister.

　　Go see what the fool is up to.

　　二、有些情况下to不能省略：

　　1. to作为不定式符号，用于省略句中，代表整个不定式短语，不能省略。如：

　　My parents encouraged me to go to college, but I didn't want to.

　　Perhaps I'll go to Brazil this summer: I'd very much like to.

　　但当want和like用于某些从句中时，其后代替整个不定式的to常可省去。这些从句主要有：when引导的时间状语从句，if和as long as引导的条件状语从句，as引导的方式状语从句，what引导的宾语从句。如：

　　Go when you want.

　　You may talk if you like.

　　2.在一些固定词组中to不能省略。如：

　　I used to like rock and roll, but now I dislike it because it's too noisy.

　　The boy is too young to know what is right.

　　He worked very hard in order to finish the work by five.

　　3.在某些带有感情色彩的不规则句子(irregular sentence)中，to不能省略。如：

　　To think that he should be so mean!

　　这类句子往往表示惊讶的语气，有时含有不赞成、不满或遗憾的感情色彩。

　　还有一些词之后可用带to的不定式，也可用不带to的不定式。如：dare，rather than, sooner than；而help之后的to的灵活使用更是人所共知。但总体来说，不带to的不定式在美国更常见。

　　其实，to的省略用法与文体也有很大关系。正式文体要求严格，该保留to还是该省略to有规定。而在非正式文体中，尤其是在口语中，to的省略现象却比比皆是，且并不影响交际。因此，我们对语言知识的学习不能仅局限在语言知识本身上，还要注意语言的实际应用。

　　(文/郑翠玲；英语辅导报大学二年级版03～04学年第21、22期；版权归英语辅导报社所有，独家网络合作伙伴新浪教育，未经许可，不得以任何形式进行转载。)