it用法归纳现将it用法归纳如下：一、指无生命、动物、植物和在性别不计或不详时指人和婴儿。

There is a person knocking at the door. Who can it be?二、指心目中的人或上文中提到的人或事物He is fifty-two, but doesn't look it.Jim is ill. Have you heard of it?三、可以代替指示代词this和thatWhat's this/that？------It's a book。

四、作无人称代词的主语，表时间、天气、距离、温度、环境和情况。

It was noisy when I got to the room.五, 表含糊概念How's it going with you? 近况如何？Does it itch much? 很痒痒吗？Where does it hurt? 哪儿疼？Whose turn is it next? 接下来轮到谁了Take it easy. 放松点！不要紧张！六、It用作形式主语替代作主语的从句、动词不定式、动名词，而把真正作主语的从句、动词不定式、动名词置于句尾。

It 作形式主语的常见句型：1. 代作主语的动词不定式，其句型为（1）It be adj. (for sb.) to do sth.（2）It be adj. of sb. to do sth.2, It替代作主语的动名词的常见句型：It’s no good/use doing…It’s (well)worth doing…It’s (well)worth one’s while doing/to do It’s (well)worth while doing/ to do3, It替代作主语的从句常见句型（1）It is + noun +从句（2）.It is adj. +clauseIt’s surprising that… (should)………竟然……It’s a pity/shame that…(should)………竟然…（3）It verb sb. + clause= It is v-ing + clauseIt+surprise/delight/inter est/disappoint/worry /please/anger sb. that…（4）It verb (to sb.) that…= sb/sth verb to do(verb = appear, seem, happen, occur, turn out)（5）It is v-ed that…=sb/sth is to do(verb=say, report, think, believe, hope, expect, know）七、It 作形式宾语用来替代作宾语的从句、动词不定式、动名词，而把真正作宾语的从句、动词不定式、动名词置于句尾。

It 作形式宾语的常见句型：1. verb+ it+ adj./noun (for/of) to do/clause (verb=think, believe, suppose, consider, keep…)八、It 常用的固定搭配1. make it(1).在口语当中相当于succeed,表示：成功、做到、说定、赶上、及时到达。

It 作形式主语时，常用于下列四种结构，且由固定译法a) it + be + noun + that-clauseit is a fact that…事实上是……it is a pity that…可惜的是……it is no good that………是没用的it is no use that…做……是无用的it is a waste of time to do…做……是浪费时间b) it + be + adjective + that-clauseit is certain that…很肯定的是……it is clear/evident that…很清楚……it is unlikely that…未必会，不见得，不太可能it is likely that…很可能……it is necessary that...有必要……c) it + be + past participle + that-clauseit is said/reported that…据说/报道……it is believed that… 据认为……；人们认为……it is believed/recognized that 普遍认为……it is well known that 大家都知道，众所周知d) it + be + intransitive verb + that-clauseit seems that/as if 好像是……it happens/happened that 碰巧……it occurs/occurred to sb that 某人想到……it looks as if 看起来好像，似乎九、习惯用法it all depends=that depends 视情况而定if it is convenient to you 如果你方面的话believe it or not 信不信由你take it easy 别着急，慢慢来，别紧张，see (to it ) that 设法使，务必做到十、it 引起的容易混淆的时间句型1、 it is/has been +段时间+since-clause"自从……以来已经多久了"，主句多采用一般现在时，从句用过去时，如果表示过去的情况，since 主句用一般过去时，从句用过去完成时，或主句用过去完成时，从句用一般过去时。

如：It's five years since they were married. (从过去算起)It is three years since his father passed away.2、 it be +段时间+before-clause段时间（long years, months, weeks, days, hours, minutes）主句中的谓语动词用肯定式，意思为："过多长时间才……"。

主句谓语动词是否定式时，意思为："没过多长时间就……"。

主句的时态可用过去时was或将来时will be，用was 时，before从句的时态用一般过去时，用will be时，从句常用一般现在时。

如It was not long before he learned those poems by heart.她没过多久就会背那些诗了。

It will be hours before he makes a decision.It will not be hours before we meet again.3、 it be +high/about 时间+that-clause此句型是个虚拟语气句型，“该做……的时候了”，此时无论主句中的be是什么时态，从句中的谓语动词一律用一般过去时或者should do，high和about是用以加强语气的。

如：It is high time that we went to school.It is time that we should make people's life a little better.4、It/This/That be the first(second/third…) time that-clause这个句型表示说话时为止某人的一种经历，关键是time前面的序数词，从句要用完成时。

This is the first time (that) these Europeans have visited the Great Wall.It was the fifth time (that) I had paid a friendly visit to America.十一、强调句型"It is/was+强调部分（主语，宾语等）+that/who+其余部分"。

It is/was+被强调部分+ that(who)… 强调句型用来强调谓语动词以外的任何句子成分。

当被强调部分是人时也可以用who。

在使用强调句型时需注意以下几点：1. 请注意强调句型的特殊疑问句如果强调的是特殊疑问句，表示"究竟，到底"等语气时，就用结构："疑问词+is/was it that +句子"，如：强调结构的一般疑问句和特殊疑问句一般疑问句形式为：Is／Was＋被强调部分＋that／who＋句子的其余部分?特殊疑问句形式为：特殊疑问词Who／When／Where／How／Why＋is／was＋it＋that＋句子的其余部分?例如：陈述句：It was you that came yesterday．一般疑问句：Was it you that came yesterday?特殊疑问句：Who was it that came yesterday?陈述句：It was last night that they had a get-together with the workers．一般疑问句：Was it last night that they had a get-together with the workers?特殊疑问句：When was it that they had a get-together with the workers?Where was it that you met him?What is it that he wants to see?When was it that you saw him?Why is it that you want to change your idea?2. 在强调原因状语从句时，只能强调由because所引导的从句。

It was because he was ill that died at once3. 在强调no t … until结构时必须把not与until一起放到被强调的位置上。

It is not until she got home that he gave her the book.4, 当被强调的部分是人时，可以用who，也可以用that；当被强调的部分是物或其他状语等时，只能用that。

5．当使用强调结构强调主语时，that／who后边的动词应和被强调的主语保持一致。