非谓语动词是指分词(包括现在分词和过去分词)、不定式、动名词等三种形式，即：
doing , done , to do , doing 。当然它们有各自不同的变化形式，如：
现在分词 doing : 有being done(被动式) ; having done (完成式); having been do
ne (完成被动式)
不定式 to do : 有to be done (被动式); to have done (完成式); to be doing(进行式)
动名词 doing : 有having done(完成式); being done(被动式) ;
非谓语动词的特点： 三种非谓语动词都具有动词的特征，虽然它们没有人称和数的变化，但是它们都能带自己的状语或有时跟宾语。它们都有各自的特征：分词具有形容词和副词的特征;动名词具有名词的特征;不定式具有名词、形容词和副词的特征。具体来讲：分词在句子中可以做定语、表语、状语或补足语等;动名词在句子中可以做主语、宾语、表语等;不定式在句子中可以做主语、宾语、表语、补足语或状语。
下面分别对三种非谓语动词进行讲解：
一．动词不定式
先看几个例句，判断不定式在句中的成分。
1.To learn a foreign language is difficult .
2. His wish is to be a driver .
3.Tom wanted to have a cup of beer .
4.The teacher told us to do morning exercises .
5.I have nothing to say .
6.They went to see their aunt .
7.It’s easy to see their aunt.
8.I don’t know what to do next .
9.I heard them make a noise .
说明：1.动词不定式作主语, 2.动词不定式作表语,3.动词不定式作宾语,4.动词不定式作宾语补足语，5.动词不定式作定语,6.动词不定式作目的状语,7.动词不定式作真正主语，it 代替动词不定式，作形式主语。8.带有连接代词的动词不定式作宾语,9.不带to 的动词不定式作宾语补足语。
掌握动词不定式应注意的几个问题：
1. “to” 是不定式符号还是介词，下列短语中的to 都是介词。
agree to object to close to , come to , lead to , refer to ,
equal to , familiar to , point to , thank to , devote to , next to , belong to , be used to , look forward to
2. 带to 还是不带to
I have no choice but to give in
I cannot do anything but give in
I saw him enter the classroom .
( 但是： He was seen to enter the classroom .)
3. 动词不定式逻辑主语是由for 作为标记的。但是有时用of .
It’s necessary for you to study hard .
It’s foolish of him to do it .
与of 连用的形容词有：
good, kind , nice , wise ,clever , foolish , right , wrong , careful , careless , polite , possible
4.后接不定式作宾语的动词有：
want , hope , wish , like , begin , try , need , forget , agree , know , promise , teach , refuse , help , arrange , dare , decide , determine , fail , manage , offer , prepare , continue , ask , mean , choose , expect etc.
需要宾语补足语的动词不能用动词不定式直接做介词的宾语，而要用it做形式宾语。例如：通常不说We think to obey the laws is important . 而说We think it important to obey the laws .
5.不定式的省略。下列短语中，如果意义明确，常常省略到to 。
want to , wish to ,hope to , like to , hate to , plan to , try to , love to , have to , o
ught to , need to , used to , be able to
6.不定式作定语，应注意两种关系：
1)动宾关系：
He has a lot of meeting to attend .
Please lend me something to write with .
He is looking for a room to live
He is looking for a room to live in .
He has no money and no place
to live ( in ) .
I think the best way to travel ( by ) is on foot .
There is no time to think ( about ) .
2)主谓关系：
She is always the last ( person) to speak at the meeting .
----I’m going to the post office , for I have a letter to post . ( 逻辑主语是I )
-------Thank you. But I have no letters to be posted now ( 逻辑主语不是I )
7.不定式作状语，可以有以下几种意义：
1) 原因
He is lucky to get here on time .
这种结构中常用的形容词有：
happy , glad , delighted , pleased , sorry , eager , anxious . lucky , fortunate , proud , angry surprised , frightened , disappointed , ready , clever , foolish , worthy
2) 目的
He came to help me with my maths .
3) 结果
I hurried to get there only to find him out .
The book is too hard for the boy to read .
He is old enough to go to school .
8 . 不定式作补足语
I saw him play in the street just now .
能跟不带to 的不定式作补足语的动词有：
see , feel , hear , listen to , look at , watch , let , have make, observe, notice
注: 当这些词为被动式时，不定式要带to , 如：
He was seen to play in the street just now.
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