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。

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。 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。