1． 作介词的to
to 有两种用法： 一为不定式+动词原形； 一为介词+名词/动名词, to 在下面的用法中是第二种，即to+ 名词/动名词：
admit to承认， confess to承认，
be accustomed to 习惯于， be used to 习惯于，
stick to 坚持， turn to开始，着手于，
devote oneself to 献身于， be devoted to 致力于，
look forward to 盼望， pay attention to 注意
2． 省to 的动词不定式
1） 情态动词 ( 除ought 外，ought to)：
2） 使役动词 let, have, make：
3） 感官动词 see, watch, look at, notice , observe, hear, listen to, smell, feel, find 等后作宾补，省略to。
注意：在被动语态中则to 不能省掉。
I saw him dance.
=He was seen to dance.
The boss made them work the whole night.
=They were made to work the whole night.
4） would rather，had better：
5） Why… / why not…：
6） help 可带to，也可不带to, help sb (to) do sth：
7） but和except：but前是动词do时，后面出现的动词用不带to的动词不定式。
8） 由and, or和than连接的两个不定式，第二个to 可以省去：
9） 通常在discover, imagine, suppose, think, understand等词后，可以省去to be：
He is supposed (to be) nice. 他应该是个好人。
举例：
He wants to move to France and marry the girl.
He wants to do nothing but go out.
比较： He wants to do nothing but go out.
He wants to believe anything but to take the medicine.
典型例题
1) ---- I usually go there by train.
---- Why not ___ by boat for a change?
A. to try going B. trying to go C. to try and go D. try going
答案：D. why not 后面接不带to 的不定式，因此选D。
2） Paul doesn't have to be made ___. He always works hard.
A. learn B. to learn C. learned D. learning
答案：B. make后接不带to 的动词不定式，当其用于被动时，to 不可省略
3． 动词不定式的否定式
Tell him not to shut the window…
She pretended not to see me when I passed by. 我走过的时候，她假装没看见。
典型例题
1）Tell him ___ the window.
A. to shut not B. not to shut C. to not shut
D. not shut
答案：B。 tell sb to do sth 的否定形式为tell sb not to do sth.
2) She pretended ___ me when I passed by.
A. not to see B. not seeing C. to not see
D. having not seen
答案：A。 pretend 后应接不定式。其否定形式为pretend not to do sth.。
3）Mrs. Smith warned her daughter ___ after drinking.
A. never to drive B. to never driver
C. never driving D. 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.
4) The boy wanted to ride his bicycle in the street，but his mother told him ____.
A. not to B. not to do C. not do it
D. do not to
答案：A。not to 为not to do it 的省略形式。可以只用to这个词，而不必重复整个不定式词组。及物动词do后应有名词、代词等，否则不对，因此B，D不对。
5) The patient was warned ___ oily food after the operation.
A. to eat no B. eating not C. not to eat
D. not eating
答案：C。warn一词要求后用不定式，此处为不定式的被动，否定形式为be warned not to do。
4． 不定式的特殊句型too…to…
1）too…to 太…以至于…
He is too excited to speak.
他太激动了，说不出话来。
---- Can I help you ? 需要我帮忙吗?
---- Well, I'm afraid the box is too heavy for you to carry it, but thank you all the same. 不用了。这箱子太重，恐怕你搬不动。谢谢您。
2) 如在too前有否定词，则整个句子用否定词表达肯定， too 后那个词表达一种委婉含义，意 为"不太"。
It's never too late to mend. (谚语)
改过不嫌晚。
3) 当too 前面有only, all, but时，意思是：非常… 等于very。
I'm only too pleased to be able to help you. 我非常高兴能帮助你。
He was but too eager to get home. 他非常想回家。
5． 不定式的特殊句型so as to
1） 表示目的；它的否定式是so as not to do。
Tom kept quiet about the accident so as not to lose his job.
汤姆对事故保持沉默是为了不丢掉他的工作。
Go in quietly so as not to wake the baby.
轻点进去，别惊醒了婴儿。
2) so kind as to ---劳驾
Would you be so kind as to tell me the time?
劳驾，现在几点了。
6． 不定式的特殊句型Why not
"Why not +动词原形"表达向某人提出建议，翻译为："为什么不……?" "干吗不……?"
例如：
Why not take a holiday?
干吗不去度假?
7． 不定式的时态和语态
时态\语态 主动 被动
一般式 to do to be done
进行式 to be doing
完成式 to have done to have been done
完成进行式 to have been doing
1) 现在时：一般现在时表示的动词，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。
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) 完成时：表示的动作发生在谓语动词表示的动作之前。
I'm sorry to have given you so much trouble.
He seems to have caught a cold.
3) 进行时： 表示动作正在进行，与谓语动词表示的动作同时发生。
He seems to be eating something.
4) 完成进行时：
She is known to have been wreaking on the problem for many years.
8． 动名词与不定式
1） 动名词与不定式的区别：
动名词表达的是： 状态，性质，心境，抽象，经常性，已发生的
不定式表达的是： 目的，结果，原因，具体，一次性，将发生的
2） 接不定式或动名词，意义相同。
3） 动名词与不定式语义不同的有11 组：
1 stop to do stop doing
2 forget to do forget doing
3 remember to do remember doing
4 regret to do regret doing
5 cease to do cease doing
6 try to do try doing
7 go on to do go on doing
8 afraid to do afraid doing
9 interested to do interested doing
10 mean to do mean doing
11 begin/ start to do begin/ start doing