非谓语动词
非谓语动词指不能单独作谓语，但仍保留动词的某些特征的动词形式。非谓语动词包括不定式、动词-ing形式和过去分词。它们没有人称和数的变化，但可以有自己的逻辑主语、宾语、状语等。
一、非谓语动词的各种形式
二、非谓语动词在句中的一些用法
1. 动词-ing形式和不定式作主语和宾语
★作主语
通常，动词-ing形式着重过程，不定式着重结果。但有时二者有下列不同之处：
1）动词-ing形式的逻辑主语可能泛指人们，而不定式的逻辑主语则常是句子中的名词或代词。
2）动词-ing形式可表示一般或抽象的多次性的动作，而不定式则往往表示具体的或一次性的动作。
★作宾语
1）有些动词后常跟不定式作宾语。这类动词常见的有agree, aim, arrange, choose, decide, demand, desire, determine, expect, fail, intend, learn, plan, manage, offer, prepare, pretend, promise, refuse, threaten, wish等。
2）有些动词后常跟动词-ing形式作宾语。这类动词常见的有admit, dislike, appreciate, avoid, enjoy, bear, escape, stand, deny, consider, mind, miss, finish, resist, imagine, risk, practice, suggest等。
2. 非谓语动词作定语
1）不定式作定语
a. 作定语的不定式与它所修饰的名词或代词在逻辑上可能是主谓关系，也可能是动宾关系。如：
The next train to arrive was from New York.
It was a game to remember.
b. 名词前有only, last, next，序数词或形容词的最高级时，其后常用不定式作定语。如：
Rita was the only person to complain.
He was the first man to fly across the Atlantic.
Alex is the best man to do the job.
c. 有些名词的同根动词后常跟不定式，因而这些名词后也常跟不定式作定语。如：
Their offer to assist in the work was not taken seriously.
（比较：They offered to assist in the work.）
2）动词-ing形式作定语可表示正在进行的动作，也可表示经常发生的或短暂的动作以及经常存在的状态。如：
The woman sending her children to school is my history teacher.
A little child learning to walk often falls.
3）过去分词作定语常表示被动或已经发生的动作。如：
We’ve met the doctors sent to work here by the city hospital.
3. 非谓语动词作表语
1）不定式作表语，常用来说明主语的具体内容。如：
His ambition is to become a successful scientist.
2）动词-ing形式作表语，可用于说明主语的内容，而且可以转换到句首作主语，常指抽象的行为；也可表示主语的性质或特征。如：
My hobby is collecting stamps. = Collecting stamps is my hobby.
The novel is very boring.
3）过去分词作表语，常表示主语的状态。如：
I was delighted to receive your gifts.
4. 非谓语动词作状语
1）不定式作状语，常表示目的、原因、结果等。不定式作结果状语时，常用于“only 不定式”结构，表示未曾预料到的或令人不快的结果。如：
A friend of mine came to see me tonight.
I jumped with joy to hear it.
Alan lifted a rock only to drop it on his own feet.
2）动词-ing形式或过去分词作状语时，可以表示时间、原因、结果、条件、让步、方式、伴随情况等，其前可加连词while, when, once, if, unless等。如：
Crossing the street, he was knocked down by a car.
Frightened by the noise outside, the little girl dared not sleep in her bedroom.
He fell off the bike, breaking his left leg.
Seen through the eyes of a young friend, Einstein was a simple, modest and ordinary man.
A group of children were sitting around the teahcer, playing games.
When heated, ice will be changed into water.
5. 非谓语动词作补语
1）动词-ing形式表示正在进行的活动或反复的动作，而不定式则表示整个活动或事件的全过程。如：
I see him passing my house every day.
I asked George to convey my best wishes to his mother.
2）感官动词和使役动词后常接省略to的不定式作宾语补足语，但用于被动语态时，需把to补出来。如：
Someone saw Mary enter the building about the time the crime was committed.
Mary was seen to enter the building about the time the crime was committed.
另外，感官动词后也可接动词-ing形式作补语，表示动作正在进行。如：
Once in the middle of the night I woke and heard the wind blowing.
