第七章 动词不定式
一.相关知识点精讲:
1. 不定式作补语
有些有动词+宾语+不定式的结构.例如:
advise
allow
cause
challenge
command
compel
drive 驱使
enable
encourage
forbid
force
impel
induce
instruct
invite
like/love
order
permit
make
let
have
want
get
warn
persuade
request
send
tell
train
urge
例如;
Father will not allow us to play on the street. 父亲不让我们在街上玩耍.
The officer ordered his men to fire. 长官命令士兵开火.
注意:有些动词如make,have,get,want等可用不定式作做宾补,也可用分词作宾补.现在分词表达主动,也表达正在进行,过去分词表达被动.
2) 有些有动词+宾语+不定式的结构,不定式的动词往往是be,不定式一般可以省去.例如:
consider
find
believe
think
declare(声称)
appoint
guess
fancy(设想)
guess
judge
imagine
know
例如:
We believe him to be guilty. 我们相信他是有罪的.
We know him to be a fool. 我们知道他是个笨蛋.(to be 不能省去)
典型例题
Charles Babbage is generally considered ___ the first computer.
A. to invent B. inventing C. to have invented D. having invented
答案:C. 一般没有consider+宾语+be以外不定式的结构,也没有consider+宾语+doing的结构,排除A,B,D.consider用动词be以外的不定式作宾补时,一般要求用不定式的完成式,故选C.
3) 有些动词可以跟there +to be的结构.例如:
believe
expect
intend
like
love
mean
prefer
want
wish
understand

例如:
We didn't expect there to be so many people there. 我们没料到会有那么多人在那里.
You wouldn't want there to be another war. 你不至于想让另外一场战争发生吧.
2. 不定式作主语
不定式作主语,往往用it作形式主语,真正的主语不定式放至句子的后面.
例如:It's so nice to hear your voice. 听到你的声音真高兴.
It's necessary for you to lock the car when you do not use it. 不用车的时候,锁车是有必要的.
It's very kind of you to help us. 他帮助我们,他真好.
It seemed selfish of him not to give them anything. 他不给他们任何东西,这显得太自私了.
但是,用不定式作主语的句子中还有一个不定式作表语时,不能用It is… to…的句型.另外,这样的句子,不能用动名词作表语.
3. It's for sb.和 It's of sb.
这样的句子中,由于表语形容词性质的不同,导致了不定式逻辑主语标志用for或of的区别.
1)for sb. 句型中的形容词一般为表示事物的特征特点,表示客观形式的形容词,如easy, hard, difficult, interesting, impossible等:例如:
It's very hard for him to study two languages. 对他来说学两门外语是很难的.
2)of sb句型中的形容词一般为表示性格,品德,心智能力,表示主观感情或态度的形容词,如good, kind, nice, clever, foolish, right.例如:
It's very nice of you to help me. 你来帮助我,你真是太好了.
用for还是用of 的另一种辨别方法:
用介词for或of后面的逻辑主语作句子的主语,用介词前边的形容词作表语,造个句子.如果通顺用of,不通则用for.例如:
You are nice. (通顺,所以应用of).
He is hard. (非所表达的意思,不通,因此用for.)
4. 不定式作表语
不定式可放在be动词后面,形成表语.例如:
My work is to clean the room every day. 我的工作是每天清扫房间.
His dream is to be a doctor. 他的梦想是成为一名医生.
5. 不定式作定语
不定式做定语通常要放在被修饰的词后,往往表示未发生的动作.例如:
I have a lot of work to do. 我有许多事要做.
There was nothing to bring home that morning. 那天早上(他回家时)两手空空.
6. 不定式作状语
1)目的状语
常用结构为to do , only to do(仅仅为了), in order to do, so as to do, so(such)… as to…(如此…以便…).例如:
He ran so fast as to catch the first bus. 他飞快地跑以便赶上第一班车.
I come here only to say good-bye to you. 我来仅仅是向你告别.
2)作结果状语,可以表示没有预料到的或事与愿违的结果,不定式要放在句子后面.
I awoke to find my truck gone. 我醒来发现箱子不见了.
He searched the room only to find nothing. 他搜索了房间,没发现什么.
3) 表原因
I'm glad to see you. 见到你很高兴.
She wept to see the sight. 她一看到这情形就哭了.
4)表示理由和条件
He must be a fool to say so.
You will do well to speak more carefully.
7.用作介词的to
to 可以用作介词,也可用作不定式的标示.下面的to 都用作介词:
admit to
object to
be accustomed to
be used to
stick to
turn to开始
look forward to
be devoted to
pay attention to
contribute to
apologize to
devote oneself to

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