It的用法及典型句型归纳一、人称代词it的最基本用法是作代词，主要指刚提到的事物，想法，以避免重复;也可以指性别不明或性别被认为是不重要的人或动物；未指明但谈话双方都明白的事情或情况。
①They watched the train until it disappeared in the distance.②Is this your dog？No, it isn’t.③I hate it when people talk with a full mouth.．二、.非人称代词.it有时并不指具体的东西而泛指天气、时间、日期、距离、价值、度量、温度、环境等：It is a lovely day, isn’t it? // It was nearly midnight when she came back.It is April First today. // It is some 3000 kilometers from A to B.It is three dollars. // Today it is 30 degrees centigrade.三、作形式主语，替代主语从句，动词不定式，或动名词短语1.作形式主语替代主语从句⑴It is clear ( obvious，true，possible，certain....) that＂┅清楚的（显然的，真的，可能的,肯定的．．．）＂⑵It is important ( necessary，right，strange，natural...) that + (should ) do (虚拟语气)┅是重要的(必要的,对的,奇怪的,自然的┅)⑶It is said (reported/ learned/believed/thought/known/told/hoped.....) that= sb / sth is said (reported/ believed /thought…) to do( to be doing/ to have done) sth＂据说（据报道，据悉．．．）＂。
⑷It is suggested ( advised/ ordered / demanded/ insisted/ commanded... ) that +(should ) do＂据建议；有命令．．⑸It is a pity ( a shame /an honour/a good thing/a fact,/a surprise/... ) thatthat后的从句一般用虚拟语气（should + 动词原形），should可省去．表示出乎意料，常译为＂竟然＂。
没有这种意义时，则不用虚拟语气。
小练一下：It is very clear that he’s round and tall like a tree.=It is important that we (learn) English well.It is necessary that he (remember) these words.It is said that he has come to Beijing.=It is reported that another earth satellite has been put into orbit.=It is suggested that the meeting ( put off).It was ordered that we (arrive) there in two hours.It is a pity that such a thing ( happen) in your class.It is a pity that he (be) ill.2.作形式主语替代不定式. ⑴It is kind ( of sb. ) to do sth.= sb be kind to do sth.一般都是表示人的特性的形容词。
如：bad /brave /careless/ clever /cruel / foolish / good （好心的）/ honest/ kind / lazy / modest/ naughty/ nice（有教养的）/polite/ rude / silly / stupid / wise ，等。
Eg. It is kind of you to give me a hand. =⑵It is necessary ( for sb. ) to do sth. .不定式的逻辑主语是由for引起。
常见的形容词有：Important/ necessary/ natural/ easy / safe / common / normal / hard / difficult / dangerous/ unusual/ rare / impossible / pleasantEg. It is important for her to come to the party.= It is important that she to the party.⑶It takes sb. ... to do sth. 常译为＂做．．．要花费某人．．．＂。
Eg It took thousands of people many years to build the Great Wall.(4)it’s up to sb to do sth 做某事由某人决定Eg It is up to us to live a green life.3.作形式主语替代动名词短语It is no good / no use / useless doing sth. “┅有好处或没有用”Eg It is dangerous walking on thin ice.It won't be any help my going with you.It is no good (learn) English without speaking English.It's useless (try) to argue with Shylock.It is a waste of time (you talk) to him.四、作形式宾语，代替不定式，动名词短语或宾语从句。
1.Sb+ think（feel/find/ consider/ take/ make/believe）+ it +necessary(important… )+( for sb. ) to do sth. /that从句Eg. The chairman thought ___ necessary to invite Professor Smith to speak at the meeting.A. thatB. itC. thisD. him翻译：她发现很难回答这个问题。
2. S+ V + it + one’s duty(an honor/ a rule…) + ( for sb. ) to do sth. /that从句Eg.I think it his duty to clean the blackboard西方国家的人们习惯为他们的亲戚朋友买圣诞礼物。
People in the west to buy Christmas presents for their relatives and friends.They want to make it clear to the public that they do an important and necessary job.3.S+ V + it + no good / no use + doing sth.我认为告诉他们没用。
We think it a waste (argue) with him4. it用在不能够直接跟宾语从句的动词后，尤其是表示好恶的动词。
如：enjoy/like/love/dislike/hate/depend on/ be fond of /see to后句型：I like (enjoy, hate…) it when….I would appreciate it if……see to(depend on/depend on/be fond of…) it thatEg I like ___ in the autumn when the weather is clear and bright.A. thisB. thatC. itD. one译：如果你能帮我，我将不胜感激I can’t help if he is always late.Please see to that you bring enough money when you go out.五、it/one/ that 三者均可用作代词，指代前面提到的名词It指代同名同物，表示特指= the+名词；one与that则指代同名异物。
One只能替代可数名词单数，表泛指= a/ an+名词；ones代替可数名词复数，泛指。
That可替代可数或不可数名词，表示特指=the+名词，多与of连用Those代替可数名词复数= the ones，多与of连用练：I have lost my umbrella; I am looking for .I haven’t a pencil. Can you lend meI prefer the red ones to the whiteMary’s handwriting is far better than of Peter.The boys in our class are more active than in your class.六、常考句型1.强调句型: It is/was + 被强调部分+ that (被强调的主语如果是人，that可以由who换用被强调的宾语是人时，用whom换用)It was Mary picked up the wallet.It was one of my old schoolmates I visited yesterday.In which play is ___ your brother appears?A. that whereB. this whenC. it thatD. it whereIt was in the lab ___ was taken charge of by Professor Zhang ___ they did the experiment.A. where; thatB. which ; whereC. that ; whereD. which; that2. It is/was not until+被强调部分+that 其中that从句中的谓语动词用肯定式。