不定式是一种非限定动词,通常由"to+动词原形"构成,如to be,to do,to combine,to expand,to get up等。下面小编告诉你英语动词不定式的结构和用法，大家一起来看看吧!
英语动词不定式的结构和用法:
1.用作主语。例如:
(1)To make you understand him completely is impossible.让你们完全了解他是不可能的。
(2)To run machines needs power.开动机器需要动力。
(3)To remember to switch off the electricity is important.重要的是要记住关掉电源。
To live is to is all there is in living.(Holmes)活着就要发挥作用,这就是生活的全部真谛。
To live of money is the root of all evil.()迷恋金钱是一切罪恶的根源。
To be ignorant of one's ignorance is the malady of the ignorant.()不知道自己的无知,是无知者的可悲之处。
To spread knowledge is to spread happiness.(Alfred Nobel)传播知识就是播种幸福。
不定式、特别是不定式短语作主语时,为了保持句子平衡,往往把主语放在句子末尾,而在它原来的位置上加上引导词it作形式上的主语。现代英语倾向于采用这种结构,尤其是当主语较长或谓语动词是被动语态或谓语动词不是系动词时,更是如此。而当句子是疑问句或感叹句时,也必须用这种结构。例如,上述(1)(2)(3)三个例子可转换为:
(1)It is impossible to make you understand him completely.
(2)It needs power to run machines.
(3)It's important to remember to switch off the electricity.
又如:
It's silly to build a wall around your interests.(Walt Disney)在自己兴趣的周围建起一座墙,是愚蠢的行为。
It is the duty of a scientist to remain curiosity.()科学家的责任是保持好奇心。
It was an easy matter to ?nd the Count when we entered the opera house.我们走进歌剧场,很容易找到了伯爵。
It's good to have you back safe and sound.你们平平安安回家就好。
It was my privilege to see her out of hers.()能参加她的葬礼是我的荣幸。
It was a good thing to work there in the little field beneath the singing larks.(Liam O'Flaherty)在地里干活,倾听着头顶上云雀歌唱,真是乐在其中。
How long will it take you to get there?(疑问句)要花多长时间才能到达那里?
What a joy it was to see her!(感叹句)见到她多么高兴!
在以it为形式主语的句子中,它所代表的真正主语有时用不定式复合结构。不定式的逻辑主语用for或of引出。
如果句子中作表语的形容词表示事物的性质,如important,necessary,possible,easy,dif?cult,hard,heavy等,用for引出。例如:
It is impossible for us to get there before lunch.我们午餐前赶到那里是不可能的。
It is necessary for you to learn from others.你必须向别人学习。
It is dif?cult for me to believe that you could so forget yourself and your
rearing.我难以相信你会这样忘记你自己和你的教养。
如果句中作表语的形容词表示人的特征、品德或意愿,如kind,honest,careless,lazy,stupid,clever,foolish,silly,sel?sh,polite,bad,generous,cruel,willing,reluctant,deliberate等,则用of引出。例如:
(4)It's very nice of you to be considerate.你真好,想得这么周到。
(5)It's careless of her to notice nothing of it.她很粗心,连这一点也没注意到。
(6)It is foolish of him to meet her again.他很愚蠢,又跟她相会。
【注】"It is+形容词+of do"句型一般可转换成一个不定式作状语的句子,语义不变;而"It is+形容词+for do"句型则不可以。例如,上述三个句子可转换为:
(4)You are very nice to be considerate.
(5)She is careless to notice nothing of it.
(6)He is foolish to meet her again.
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2.用作表语。例如:
Her wish was to become a teacher.她的愿望是当个教师。
To know everything is to know nothing.样样都懂,样样稀松。
There are two tragedies in is not to get your heart's
other is to get it.()人生有两种悲剧:一种是得不到你想要的东西,另一种是得到了你想要的东西。
To enlarge or illustrate this power and effect of love is to set a candle
in the sun.(Robert Burton)用笔墨叙述爱情的这种力量和影响,无异于在阳光下点燃一支蜡烛。
What we want is to learn from practice.我们需要的是向实践学习。
用介词for引出不定式的逻辑主语的不定式复合结构,可作表语;这时,句中的主语是不定式的逻辑宾语。例如:
A lecture on high-energy physics will be for Professor Bryce to deliver.高能物理演讲将由布赖斯教授来做。
在用不定式作表语的句子中,系动词除be外,还有seem,happen,appear,get,pretend等。例如:
He seems(appears)to be living in the area.他似乎是住在这个地区。
He appears to have caught cold.他似乎是伤风了。
She pretended not to see him.她装作没看见他。
句中如果主语部分有实义动词do的各种形式,作表语的不定式实际上是do的引申,即表示do所做的内容,这时不定式可省略to。例如:
The least I can do is(to)write to you.我至少能做到的是给你写信。
What the plan does is(to)ensure a fair pension for all.实施这项计划就是保证给所有的人一笔可观的救济金。
The only thing I can do now is go on by myself.我现在能做的事就是自己继续进行下去。
两种不同性质的“be +不定式”结构:
【问题】以下两组句子，be之后都是动词不定式，请问它们有何区别?
第一组:
Her job is to look after the children. 她的工作是照顾这些孩子。
My aim is to start up my own company. 我的目标是开办一家我自己的公司。
His ambition was to meet his favourite pop star face to face. 他的心愿是，要面对面地见到他所喜爱的流行歌星。
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第二组:
He is to stay here until we return. 在我们回来之前他必须呆在这里。
Such people are to be pitied. 这种人应受到怜悯。
If we are to succeed, we must rely on the masses. 我们要成功必须依靠群众。
英语中，“不定式作表语”和表将来的“be +不定式”结构，是两个不同的概念。第一组是“不定式作表语”; 第一组是表将来的“be +不定式”结构。我们用最简单的方法做一区别，请看这两个句子:
Her job is to look after the children. 她的工作是照料这些孩子。
She is to look after the children. 她将要照料这些孩子。(表将来，可能是安排的任务)
这两句话只是主语不同，其他部分看起来完全一样，意思却大不相同，这是为什么?
它们看起来太相似了，以至于有时难以区别，这确实是一个很有意思的问题。
Her job is to look after the children. 意为 “她的工作是照料孩子的。” 本句中，is 是系动词，to look after children是不定式作表语。主语和表语可以互换而意思保持不变:To look after the children is her job. (照料孩子是她的工作。)
She is to look after the children. 意为“她将要照料孩子。”本句中，is是助动词，跟不定式to look一起，表示将来。因为不是主系表关系，所以is前后两部分不能颠倒，不可以说:To look after the children is she.
问题中的第一组都可以“主表颠倒”，变成:
To look after the children is her work. 照顾这些孩子是她的工作。
To start up my own company is my aim. 开办一家我自己的公司是我的目标。
To meet his favourite pop star face to face was her ambition. 面对面地见到他所喜爱的流行歌星是他的心愿。
第二组则不可以颠倒，因为颠倒后句意逻辑不成立。
【判断规则】A代表“主语”，B代表“不定式”:
“主系表结构”:A is B. 可以说:B is A. (is意为“是”)
“将来时结构”:A is B. 不可以说:B is A. (is to do意为“将要做”)
不定式和现在分词作结果状语的区别:
不定式和现在分词均可用结果状语，但两者用法有区别:
(1) 现在分词用作结果状语
通常表示一种自然的结果，即属预料之中的事。如:
He died, leaving his wife with five children. 他死了，留下他妻子和五个儿子。
The child fell, striking his head against the door and cutting it. 那孩子跌倒了，头碰在门上磕破了。
(2) 不定式用作结果状语
主要表示没有预料到的情况或结果，即属预料之外的事。该用法通常与副词only连用。如:
He lifted a rock only to drop it on his own feet. 他搬起石头砸了自己的脚。
He hurried to the house only to find that it was empty. 他急忙赶到那所房子，却发现空无一人。
She got there only to be told that they had gone on holiday. 她到达那里，被告知他们度假去了。
注意:并非所有表示结果的不定式都含有这种“意外”的效果。如:
What have I done to offend you. 我干什么惹你生气了?
The tea is too hot to drink. 茶太热，不能喝。
busy后接不定式还是现在分词:
1. 用作形容词时，be busy后面习惯上要接现在分词，不能接不定式。如:
She is busy gathering data. 她正忙着收集数据。
The bee are busy making honey. 蜜蜂正忙于采蜜。
He is busy getting ready for his journey. 他正忙着为旅行作准备。
Farmers were busy getting in the crops. 农民在忙着收庄稼。
I’ve been busy weeding the garden. 我一直在园子里忙着除杂草。
She was busy spinning cotton into thread. 他忙于将棉纺成纱。
She’s busy reviewing her lessons for tomorrow’s exam. 她在忙于复习功课，准备明天的考试。
2. busy用作动词时，通常用于busy oneself doing sth，其中的现在分词也不能换成不定式。如:
He busied himself (with) answering letters. 他忙于回信。
He busied himself (in) cooking the dinner. 他忙着做饭。