非谓语动词之“动词不定式”详解
非谓语动词就是不充当谓语的动词，分两种。一是动词不定式。二是动词ing形式。
1）作主语
To learn English well is not easy. 或It is not easy to learn English well.
[说明]动词不定式作主语时，往往用it作形式主语，这种句型可归纳为下面的句型：
e.g. It is + adj.+ 动词不定式
如果要说明不定式表示的动作执行者，可以用for+sb.
e.g. It is + adj.+ for sb.to do sth.
2）作表语
（表语用来说明主语的身份、性质、品性、特征和状态的，表语常由名词、形容词、副词、介词短语、动词的-ing形式、不定式、从句来充当，它常位于系动词（be, become, appear, seem, look, sound, feel, get, smell等词）之后。）
e.g. My wish is to become a teacher.
3）作宾语或者宾语补足语
e.g. Most of us like to watch football matches.
e.g. He told me to be here on time.
4）作定语：e.g. I have nothing to say about that thing.
5）作状语：e.g. He stopped to have a look.
[说明] 动词不定式的否定形式：not + to + 动词原形构成
e.g. He asked me not to make such a mistake.
2、动词不定式与疑问词连用：
疑问词who, what, which和疑问副词when, where, how, why等后面可以按动词不定式，构成动词不定式短语。
e.g. (1) He doesn’t know how to use the machine.
(2) How to use the machine is a question.
(3) The question is when to go there.
3、省去了to 的动词不定式
1）let, have, make+do
2）感官动词see, watch, look at, notice, hear, listen to, smell, feel, find +to。
注意：在被动语态中则to 不能省掉。
e.g. I saw him dance. =He was seen to dance.
e.g. The boss made them work the whole night.=They were made to work the whole night.
3）would rather，had better + do
4、动词不定式的特殊句型：
1）too…to…+to do：e.g. He is too excited to speak.
2）enough to do： e.g. The child is old enough to go to school.
3）Why not +do e.g. Why not take a holiday?
4）so as (not) to do: 表示目的 e.g. Go in quietly so as not to wake the baby.
5、不定式的难点：
1）用作介词的“to”：
比如说look forward to ; pay attention to; devote oneself tobe/get used to，后面都是+doing的！2）It's for sb.和It's of sb.的区别
动词ing形式分为两种，一是动名词，二是现在分词
1．动词的-ing形式用作动名词：
动名词是动词的一种非谓语形式，由动词原形加-ing构成，它在句中起名词的作用，可以在句子中用作主语、表语、宾语、宾语补语、状语和定语。
1）动名词作主语： e.g. Walking is good exercise. 走路是很好的运动
2）动名词作表语 e.g. My favorite sport is swimming. 我最喜欢的运动是游泳。
3）动名词作宾语： e.g. Jim dislikes eating chocolate. 吉姆不喜欢吃巧克力。
e.g. She can’t help crying at a sad movie. 她看了忧伤的电影禁不住要哭。
[说明] 有些动词和动词短语只能接动名词。
e.g.admit, finish, forgive, give up, mind, practise, be good at, do well in, can't help, keep on, feel like, be used to, look forward to, prefer to,。
6）动名词作定语：动名词可以单独作定语，就像形容词一样。
e.g. a smiling face 笑脸swimming pool 游泳池dining-car 餐车
2．动词的-ing形式用作现在分词：
-ing分词通常用作宾语补足语，表示动作正在发生或者正在进行。这种用法通常用在下列动词中：see, hear, find, smell, watch, find, listen to, look at, notice, observe
e.g.1）There we found him watching TV. 我们发现他在那儿看电视。
2）I heard someone knocking at the door. 我听见有人在敲门。
3．动词ing形式和动名词之间的比较：
下面这些动词，后面接不定式或动名词意思是不一样的：
【专练】
1. Don't forget _________ the letter.
A. to send
B. send
C. sending
D. being sent
2. The chair looks very old, but in fact it is very comfortable to _________.
A. sit
B. sit on
C. be sat
D. be sat on
3. Is ______ necessary to return the book tomorrow?
A. this
B. that
C. it
D. which
4. I'm afraid they would not allow him ________ here.
A. to smoke
B. smoking
C. smokes
D. smoke
5. Mother told me ________ the water before I drank it.
A. boiling
B. boiled
C. boil
D. to boil
