一．不定式：
一）不定式的常考形式：
1)
一般形式：He decided to work harder in order to catch up with the others.
被动形式: He preferred to be assigned some heavier work to do.
语法功能：
表示与谓语动词同步发生
2)
完成形式：He pretended not to have seen me.
被动形式：The book is said to have been translated into many languages.
语法功能：表示发生在谓语动词之前
二）不定式常考的考点：
1）不定式做定语----将要发生
2）不定式做状语----目的
3）不定式充当名词功能---To see is to believe.
三)不定式的省略
1)感官动词 see, watch, observe, notice, look at, hear, listen to, smell, taste, feel
+ do 表示动作的完整性，真实性；
+ doing
表示动作的连续性，进行性
I saw him work in the garden yesterday.
昨天我看见他在花园里干活了。(强调"我看见了"这个事实)
I saw him working in the garden yesterday.
昨天我见他正在花园里干活。（强调"我见他正干活"这个动作）
v
感官动词后面接形容词而不是副词：The cake tastes good; It feels comfortable.
2) 使役动词
have bid make let 等词后不定式要省略但同1)一样被动以后要还原to
I ‘d like to have John do it.
I have my package weighed.
Paul doesn’t have to be made to learn.
3) help
help sb do
help sb to do
help do
help to do
四)有些动词后只跟不定式如：
want，wish，hope，manage，promise，refuse，pretend，plan， offer，decide，agree，expect
allow sb to do,
cause sb to do , permit sb to do, enable sb to do
force sb to do. be more likely to do
love to do
warn sb to do
be able to do
be
ambitious to do. begin to do . start to do
五) 有的时候to后面要接-ing形式
accustom (oneself) to; be accustomed to; face up to; in addition to; look forward to; object to; be reduced to; resign oneself to; be resigned to; resort to; sink to; be used to; be alternative to; be close/closeness to; be dedication/dedicated to; be opposition/opposed to; be similarity/similar to.
三、need/want 后的-ing形式具有被动的意思。其中，want不太常用。
He needs (a lot of) encouraging.
