it用作代词,意为“它”,既可以指物,也可以指人。it作人称代词,可以用来代替一个名词、短语、从句或句子,以避免它们在句中的重复。这时可以指提到过的,也可以指未提到过的,在句中作主语、表语或宾语。
1)指事物,it可以指代除人以外的一切事物或动物。如:
I dropped my watch and it broke.
我把手表掉在地上摔坏了。
2)指人,it指人主要用于指性别不明的婴儿或只听其声而不见其人的人。如:
Is it a boy or a girl?
是男孩还是女孩?
There is a knock on the door.It must be the postman.
有人在敲门,一定是邮递员。
-“Listen.Someone is crying.”
-“Oh,it must be Mary.”
“听,有人在哭。”
“噢,一定是玛丽。”
3)代替某些代词
代词it还可用于代替指示代词this,that以及复合不定代词something,,anything,nothing等。如:
“What's this”
“It's a new machine.”
“这是什么?”
“是一种新机器。”
1)it 作非人称代词主要用来指时间、距离、价值、天气、气候及温度等自然现象。如:
It's too late to go there now.
现在去那儿已经太迟了。
It rained all day yesterday.昨天下了一天的雨。
2)用于某些句型,如:
It's time for sth.
该做某事了。
It's time to do sth.
是做某事的时候了。
It's time for sb to do sth.
某人该干某事了。
It's time+that-从句.
某人该做某事了。(从句谓语用过去式,有时也用“should+动词原形”)
It's first(second)time+that-从句.
某人第几次干某事。(从句谓语用现在完成时)
It 's+时间段+since-从句.
自从……以来有一段时间了。
It 's+时间段+before-从句.
过多长的时间才……
1)当不定式、动名词、从句等复杂成分作句子主语时,为保持句子平衡,通常把真正的主语放在句末,而在句首使用形式主语it。如:
It's very important to remember this.
记住这一点很重要。
It's hard work climbing mountains.
爬山是费劲的事。
It's unknown when he will come.
他什么时候来还不知道。
2)it用作形式主语的重要句型。如:
①It+be+adj.+for (of) sb to do sth.某人做某事……
It is hard for him to make up his mind.
他很难下定决心。
Ir was foolish of her to say such a thing.
她说那样的话,真是太蠢了。
温馨提示
此句型中的介词of与for的区别是:of用于指某人的性格、属性、特征等,介词for表示对象,意为“对……来说”。
②It takes sb+时间段+to do sth.某人做某事花了……时间
I took me two hours to finish my homework.
做作业花了我两个小时的时间。
③It is up to sb to do sth.该由某人做某事了。
It's up to you to make the choice.
得由你来作选择。
④lt looks(sems,appears,
happens,occurs)that (as if).…似乎……
Ir seemed as though he didn't recognize me.他似乎没认出我来。
1)当不定式、动名词、从句等复杂成分用作宾语且其后跟有宾语补足语时,通常会在宾语补足语前使用it 作为形式宾语,而将真正的宾语移至句末。其基本结构为“动词+it宾语补足语+不定式(动名词或从句)”。如:
I find it difficult to do the job well.
我发现做好这件事不容易。
I think it best that you should stay here.
我认为你最好住这儿。
We think it no use complaining.
我们认为抱怨是没有用的。
2)用作形式宾语的几个特殊结构
①动词+it+that-从句。如:
I take it (that)he will come on time.
我认为他会准时来的。
②动词+it+when(if)-从句。如:
We really appreciate it when she offered to help.她来帮忙了,我们十分感激。
③动词+prep.+it+that-从句。如:
I can't answer for it that he will come.
我不能保证他会来。
④动词+it+介词短语+that-从句。如:
I took it for granted that he would help us.
我认为他会帮助我们的。
it在强调句中的用法强调句的基本结构是:It+be+被强调部分+that(who)+其他部分。如:
It was a computer that he bought last week.
他上个星期买的是一台电脑。