动词不定式

用作介词的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

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.