初一至初三下册公办英语教材重点知识

初一下册重点知识
一、语法知识：
1）一般现在时：肯定句、否定句、一般疑问句
第三人称单数动词变化规律（。

）
2)情态动词can的用法: 肯定句、否定句、一般疑问句
特殊疑问句（What can you do?）
3日期表达法：in 2010；on July 25\on 25 July（（读法）
4)时刻表达法：at 10 o’ clock; at 19:15 ; at 10:30（读法）
5)序数词：基数词-------序数词(1-31)
基数词：
1、3——19后缀-teen结尾，单词有两个重音。

要特别强调thirteen
fifteen eighteen 的发音和拼写。

2、0——90后缀-ty结尾。

3、十位数和个位数之间需用连字符号“—”。

序数词：
1、词1—19除第一（first），第二（second），第三（third）有特殊
形式以外，其余均有在基数词后加—th构成。

2、意fifth eighth ninth twelfth 的拼写
3、位整数的序数词的构成:在基数词的词尾—ty 中的y变为i,然后
加—eth.
4、十几变为序数词时，仅将个位变为序数词，十位数不变。

5、序数词的缩写形式：1st2nd 3rd 4th 5th…
6）名词所有格：teacher’s room teachers’ room
my father’s telephone number(读音)
7)There be ….句型的用法
There be ＋sb．（sth）＋doing sth．＋地点／时间状语
There are several children swimming in the river．
There is a wallet lying on the ground.
二、主要句型：
1）When is your birthday? When do you have math?
2) What kind of movies do you like?
What kind of noodles would you like ?
3) What time is it?（What’s the time?）
4) What’s your favorite subject?
What subject do you like best?
5) Why do you like P.E?Because….
6) Who is your English teacher?
7 )Where are you from? Where do you come from? Where do you live? What’s your address? Where’s the post office?
8) There is…. ; There are….
There isn’t…. ; There aren’t….
Is there…? Are there…?
9) Here is(a,an)…. Here are….
(Here it is. Here you are.)
((not…any\not…a\an \no)
10) What does he do? What’s she?
What do you want to be?
11)What size bowl of noodles would you like?
12)Do you want…? I don’t want….
13)I think it’s boring. I don’t think it’s boring.(She thinks it’s boring) （think, believe, suppose, expect, fancy, imagine等动词后面宾语从句的否定词转移到主句中，即主句的谓语动词用否定式，而从句的谓语动词用肯定式。

）
I don't think I know you.我想我并不认识你。

I don' t believe he will come.我相信他不回来。

三、词组：
get up go to school(work) eat(have)dinner do homework go to bed
next to across from in front of have an Art Festival go to a movie
(see a movie) on weekends help sb with sth take a bus(taxi)to…
play the guitar(piano,drums,trumpet…) do Chinese kung fu listen to
get home go home take a shower have math(science…) on Sunday(…)
at about(round )7 o’clock be strict with sb(in sth) call sb at 5669678
be busy(tired;quiet) be friendly to sb(be good with sb) play basketball(…) write to sb have fun turn left(turn to the left) on the (one’s)left(right)
in the neighborhood
四、任务训练：1、Ask for and give directions on the street
2、Order food
3. Take about job
4. Talk about countries、nationalities and languages
5. Talk about abilities
6. Talk about dates
7. Talk about daily routines,ask about and say times.
8.Talk about preferences.Give the reasons or make plans.
9.Talk about jobs.
五、单词：1.months of the year:
January February March April May June July August September
October November December
2.days of the week:
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
3.subjects:
math science history physical education(P.E.) art music
4.countries:
Canada France Japan the United states
Australia Singapore the United Kingdom
5.job:
doctor reporter policeman waiter bank clerk
shop assistant actor
6:movies:
a comedy a thriller an action movie a romance
7、animals:
tiger elephant koalas dolphin panda lion penguin giraffe
8.food and drink:
noodles beef chicken mutton potatoes cabbage dumplings
porridge soup green tea orange juice
9.place:
post office restaurant bank supermarket avenue pay phone
park zoo hotel library
初二下册重点知识
一、语法：
1）形容词、副词比较级、最高级：
形容词、副词比较级、最高级规则变化
句型：He has shorter hair than Sam.
It has the biggest screens and the most comfortable seats.
I’m more outgoing than my sister
形容词、副词原级比较：Liu Ying is(not)as good at sports as her sister.
比较状语从句:
通常由as, than, as (so)...as等引导,一般省略从句的谓语部分,只剩下名词或代词(用主格或宾格均可)。

Jane is much taller than I/me.
I don’t have as many books as you (do).
Which is longer,this ruler or that one?
Which is the biggest,the sun,the moon or the earth?
The Changjiang River is one of the longest rivers in China.
This book is as interesting as that one .
He doesn’t run as\so fast as his brother.
Our city is becoming more and more beautiful.
The harder you work,the more you’ll learn.
注意以下句子：
1、The Yellow River is the second longest river in China.
2、This book isn’t as interesting as that one.
This book is less interesting than that one.
3、This is the shortest of the two roads.(口语)
He is the taller of the two.
4、He is the tallest student in our class.
Nobody else in our class is taller than he (is).
He is taller than any other student in our class.
any of the other students in our class.
any of the others in our class.
1、Shanghai is larger than any other city in China.
China is larger than any country in Africa.
2、In winter the weather in the north is colder than that in the south.
The books on the desk are cheaper than those on the shelf.
2) 复习一般过去时、学习动词过去式不规则变化:（肯定句、否定句、一般疑问句）
初中英语不规则动词过去式、过去分词表
（1）AAA型（动词原形、过去式、过去分词同形）
cost（花费）cost cost cut（割）cut cut
hit（打）hit hit hurt 伤害）hurt hurt
let（让） let let put（放） put put
read （读） read read
(2) AAB型（动词原形与过去式同形）beat（跳动） beat beaten
(3) ABA型（动词原形与过去分词同形）
become（变成） became become come（来） came come 、
run（跑）ran run
(4) ABB型（过去式与过去分词同形）
dig（挖） dug dug get（得到） got got
hang（吊死）hanged hanged hang（悬挂） hung hung
hold（抓住） held held shine（照耀）shone shone
sit（坐）sat sat win （赢） won won
meet（遇见）met met keep （保持）kept kept
sleep（睡）slept slept sweep（扫）swept swept
feel（感觉）felt felt smell（闻）smelt smelt
leave（离开）left left build（建设）built built
lend（借出） lent lent send （传送) sent sent
spend（花费）spent spent lose （丢失） lost lost
burn （燃烧）burnt burnt learn（学习）learnt learnt
mean（意思是） meant meant catch（抓住） caught caught
teach（教） taught taught bring（带来） brought brought
fight （战斗） fought fought buy（买） bought bought
think（想）thought thought hear （听见）heard heard
sell（卖）sold sold tell（告诉） told told
say（说） said said find（找到） found found
have/has（有） had had make（制造）made made
stand（站）stood stood understand明白understood understood (5) ABC型（动词原形、过去式与过去分词三者不同形）
begin（开始）began begun drink（喝）drank drunk ring（铃响）rang rung sing （唱）sang sung swim（游泳）swam swum blow（吹）blew blown draw （画）drew drawn fly（飞）flew flown grow（生长） grew grown know（知道） knew known throw（投掷）threw thrown show（出示）showed shown break（打破）broke broken choose（选择）chose chosen forget（忘记） forgot forgotten (forgot) speak（说，讲）spoke spoken wake（醒）woke woke drive（驾驶）drove driven eat（吃）ate eaten fall（落下）fell fallen give（给）gave given rise（升高） rose risen take（取）took taken mistake（弄错） mistook mistaken ride（骑）rode ridden write（写）wrote written
do（做）did done go（去）went gone
lie（平躺）lay lain see（看见）saw seen wear （穿）wore worn be ( am, is, are )（是）was, were been 3）一般将来时：be going to、will\shall---won’t\shan’t
4) till \until的用法
I slept until midnight.
Wait till I call you.
· I can't come until tomorrow.
She didn't arrive until 6 o'clock.
Don't get off the bus until it has stopped.。

Until可用于句首，而till通常不用于句首。

Until you told me, I had heard nothing of what happened. Until then, I knew nothing at all about it.
5）could 的用法：Could y ou sweep the floor?
Could I borrow the books?(can)
6)反意疑问句：It is a nice day, isn’t it?
It looks like rain,doesn’t it? EXERCISES:
1.There are few people in the room, ?
2.She is too young to go to school, ?
3.She can hardly hear you, ?
4.Tom has never been to Beijing, ?
6.There is little water in the bottle, ?
7.There is a tree in front of the building, ?
8.Something is wrong with your computer, ?
9.Anything is possible in the world, ?
10.Everything is ready, ?
11.Somebody wants to see you, ?
12.Everybody likes her very much, ?
13.This is a beautiful picture, ?
14.Those aren’t banana trees,?
15.That is a useful book, ?
16.These are nice apples, ?
17.Tom has a new watch, ?( )?
18.Peter has to help her mother at home, ?
19.They had a good time in Beijing, ?
20.We’d better stop talking,?
21.Lucy has ever been to Japan, ?
22.We need to arrive in America at 8:00, ?
23. That girl must be Mary, ?
24.It must have rained last night,_________?
25.I’m right,?
26.Listen to me carefully, ?
27.Don’t play with fire,?
28.Let’s go to the park,?
29.Let us help you, ?
30.She said he would come tomorrow, ?
31.He told us how to find the building, ?
32.I think she is a good girl, ?
33.They don’t think she is right,?
34. We don’t think she is right,?
35.It’s unfair,____________?
36. You'd like to go with me, __________?
7)复习现在进行时：(现在分词的构成)
8）have to(has to\had to)----must
You must stay here until 8 o’clock tomorrow morning.
You will have to stay here until 8 o’clock tomorrow morning.
Do you have to stay until 8 o’clock?
You don’t have to worry about your study.
You needn’t worry about your study .
二、句型：1）When were you born?
2)When did she become a movie star?
3)What are you doing for vacation?
4)When areyou going?
5)What are you going to be when you grow up?
I’m going to be a basketball player.
6)How are you going to do?
7) Could you please…?
Can you please…?
8)Were there any sharks?No, there weren’t any sharks.
9)What’s today? What’s the date today?
10)She’s a little more outgoing than me.
My friend is the same as me.
三、词组：
go to a doctor have a piano lesson too much next week(…)
the day after tomorrow keep quiet(be quiet) the whole day(all day) be free look the same be good at make sb laugh most of turn on pour…into two teaspoon of…put…into add…to two slices of bread
go to the beach(aquarium…) have a great(good wonderful)time\have fun
at the end of…day off go for a drive (never)too…to…
spend sometime (in)doing\on sth take part in send sb sth\send sth to sb
go fishing(hiking sightseeing shopping swimming) show sb sth\show sth to sb grow up at the same time all over the world keep fit have a test work on invite sb to do sth(invite sb to somewhere) take care of do a survey of
think about in northern(southern…)China\in the north(south ) of China
wait in line be friendly to sb feel like sth(doing sth) show …around…
be careful (to do sth) ask sb to do sth tell sb sth (tell sth to sb) cut up not…at all in common mix up major in do chores(do housework)
do the laundry(do some washing) do the dishes take out make one’s bed look through come along get along at least get back
四、任务训练
1）Talk about obligations.
2) Talk about personal traits.
3)Discrible a process.
4) Talk about events in the past.
5) Talk about famous people.
6) Talk about future intentions.
7)Make polite requests.Ask for permission.
8)Discuss preferences.
9)Make small talks.
初三下册重点知识
一、语法：
1、现在完成时:already yet ever never for since …)
（肯定句、否定句、一般疑问句、划线提问how long）
1)过去分词规则和不规则的变化。

2)延续动词与非延续动词的转换（for since）
leave --- be away(from), borrow --- keep, buy --- have,
begin/start --- be on, die --- be dead, finish --- be over,
join --- be in+组织机构, be a member of+组织机构,
open ---be open, fall ill --- be ill, get up---be up,
get\catch a cold --- have a cold, come here --- be here,
go there --- be there, become --- be,
come back --- be back, fall asleep --- be asleep,
get to/ arrive/reach --- be (in), ,
get to know --- know, go (get) out →be out，
put on→ wear；
hear from\get \recieve a letter from—have a letter
close—be closed move to---live in
go to school—be a student
3)have\has been have\has gone 的区别
4)句型的转换（初三下---初四）
He has joined the Party.
He has been in the Party for two years(since 2008).
(since two years ago).
He has been a Party member for two years (since 2008).
(since two years ago).
It’s(has been)two years since he joined the Party.
Two years has passed since he joined the Party.
一般过去式与现在完成时的区别：
1）现在完成时：强调与现在的关系。

2）一般现在时：强调过去的动作和存在的状态。

I had breakfast at six this morning .
I have had breakfast.
现在完成进行时：主要是现在完成时和现在完成进行时的区别：
1.现在完成进行时更强调动作的延续性，它是现在完成时的强调形式。

He has rung me up five times since 12 o’cl ock.
He has been ringing me up all morning.
2.在不用时间状语的情况下，现在完成进行时表示动作仍然在进行，
而现在完成时表示动作已结束。

The students have been preparing for the exam.
(动作还在进行)学生们一直在准备考试。

The students have prepared for the exam.
学生们为考试做了准备。

3.有些表示状态、感情、感觉的动词，如：have like hate hear
know believe等动词，不能用于现在完成进行时，但可以用于现在
完成时。

They have known each other since 1990.
(现在完成进行时基本上没有否定结构)
2、used to do:
used to + do："过去常常"表示过去习惯性的动作或状态，但如今已不存在。

Mother used to be forgetful.
Scarf often used(often) to take a walk，but not now.
否定式简写为usedn't \usen’t\didn’t
We usedn’t to go there every year.
We didn’t use to go there every year.
疑问式：
1)He used to go to market every Sunday.
Used he to go to market every Sunday?No,he usedn’t to.\Yes,he used to.(英) Did He use to go to market every Sunday?No,he didn’t.\Y es, he did.（美）2)There used to be a temple on the mountain.
Used there to be a temple on the mountain?
Did there use to be a temple on the mountain?
3)You used to live in Qingdao,usedn’t you?\didn’t you?
4)Usedn’t you to like it?
Didn’t you use to like it?
used to,would
两者都可以表示过去经常重复的动作。

在表示过去的习惯时，used to用于较规则的习惯。

此外，used to有时侧重于和现在相对照，既含有过去经常怎样，而今已不怎样之含义。

The old man used to smoke.
She used to live in the countryside.
would 通常表示过去发生的习惯动作，多具有一种回想的心情，不含对比的含义，常带有时间状语，有时还表示自愿的动作和行为，或表示过去某一令人讨厌的习惯动作。

She would see him on Sundays.
I would ask her for help when I met with difficulties.
He would tell the same story over and over again.
would表示反复发生的动作。

如果某一动作没有反复性，就不能用would，只能用used to。

例如：
And from that day on，as soon as the table was cleared and the dishes were gone. Mother would disappear into her sewing room to practice.
从那天起，只要碗盘撤掉、饭桌一清理干净，妈妈就马上躲进做针线活的房间练习起来。

(具有反复性)
I used to live in Beijing．我过去住在北京。

(没有反复性)
used to表示过去经常性或习惯性的动作或状态现在已经结束，would则表示有可能再发生。

如：
People used to believe that the earth was flat．
过去，人们总以为地球是扁平的。

(现在已不再这样认为)
would与used to都不能用来表示动作发生的具体频度或具体的一段时间。

例如，不能说：
（3）I would/used to go to France six times．
（4）He used to live in Africa for twenty years．
上两句应改成：
（5）I went to France six times．我去过法国6次。

（6）He lived in Africa for twenty years. 他在非洲住过20年。

be used to + doing：(be accustomed to) 对……已感到习惯，或"习惯于"，to是介词，后需加名词或动名词。

He is used to a vegetarian diet.
Scarf is used to taking a walk.(现在习惯于散步)
3、被动语态：
被动语态：教师要掌握：被动语态的时态只有十个，四个完成进行时（现在、过去、将来、过去将来完成进行时）、将来进行时、过去将来进
行时没有被动语态。

1)各时态被动语态的构成
一般现在时：am／is／are＋p．p．
一般过去时：was／were＋p．p．
一般将来时：shall ／will be ＋p．p．
现在完成时：have ／has been ＋p．p．
现在进行时：am／is／are＋being＋p．p．
过去将来时：should ／would be ＋p．p．
含情态动词的被动结构：情态动词＋be＋p．p．
2)双宾语的被动语态：
To:send show bring write tell pay offer teach pass give…
For:make draw order sing get find cook…
3)动词make see hear watch notice 等动词后省掉to 的动词不定式，变被动
语态要加上to 。

I often see Tom come out of the lab.
Tom is often seen to come out of the lab.
4)复合宾语的被动语态：只将复合宾语中的逻辑主语变为主语，其余部分不
变。

We found him in the room just now.
He was found in the room just now.
5)主动语态的谓语动词为短语动词时，改为被动语态时，要注意不要漏掉介词或副词，以保持短语动词的完整性。

They took good care of these books .
These books were taken good care of by them.(Good care was taken of these books by them)
注意以下句子的被动语态：
1、Our town has built a lot of buildings in the past few years.
A lot of buildings have been built in our town in the last few years.
2、I had to do my homework at home.
My homework had to be done at home .
3、He happened to meet Tom in the street.
Tom happened to be met in the street.
4、We used to do it this way.
It used to be done this way.
5、John seems to told Mary something about the accident.
Mary seems to be told something about the accident.
6、Nobody has ever spoken to me like that.
I have never been spoken to like that.
7、Who has broken the cup？
By whom has the cup been broken？
Whom has the cup been broken by？
8、What will they do to help him out?
What will be done to help him out?
9、He is sure to finish the job by then.
The job is sure to be finished by then.
定语从句（限制性定语从句）which that who
1)定语从句的位置：放在名词或代词的后面。

2)被修饰的名词或代词称为先行词；引导定语从句的连接词称为关系词,
that、which、who、whose关系代词
where、when、how、why关系副词。

This is the thief (that/who/whom) we have been looking for these days.
Please find a room which is big enough for all of us to live in.
This is the room where they had a meeting a week ago.
I can never forget the day when I first saw you.
教师要掌握：* 在以下情况下只能用that,而不能用which
1）当先行词为all,any,few,little,anything,everything,nothing;或被它们修饰时：
Is there anything (that)I can do for you?
All that can be done must be done.
He asked few questions that the teacher asked.
2)当先行词被序数词修饰时（last）：
This is the first two-story bus that runs in our city.
The last place that we visited in Beijing is the Summer Palace.
3)当先行词被形容词最高级修饰时：
This is the most exciting football game that I’ve ever seen.
4) 当先行词被the very,the only,the same等修饰时：
That’s the only thing that we can do now.
These are the very words that he used.
5)当引导定语从句的关系代词在句中作表语时：
China isn’t the country that it was.
* 当主语以who\which开头，定语从句的引导词用that ，不用who\which,避免重复.
Who is the girl that spoken to you just now?
Which is the car that was made in Shanghai?
* 在限制性定语从句中that可代替when\where\或why,表示时间、地点、原因（可省略）;关系副词when where why的含义相当于“介词+which”.
1)Beijing is the place where I was born.
in which I was born.
which I was born in
(that)I was born.
2)Is this the reason why you refused us?
for which you refused us?
which you refused us for?
(that)you refused us?
3)I’ll never forget the day when I joined the Party.
on which I joined the Party.
which I joined the Party on.
(that)I joined the Party.
* whose用于指物，有时可与which 交替使用，通常的词序是名词词组+of which He lives in the house whose windows are blue.
the windows of which are blue.
5)So\ neither \nor
He cleaned his room.So did I.
They will flying to Shanghai next week.So will we.
He didn’t do the homework yesterday.Neither did I.\Nor did I.\Me neither.
*It’s a fine day.So it is.
She plays the piano wonderfully.So she does.
neither…nor…\either …or\neither\either\each\every
Neither you nor I am a teacher.
Neither knife is sharp.
Either I or you are a teacher.
My father will come either today or tomorrow.
I arrived there on time. He arrived there on time,too.
I didn’t arrive there on time. He didn’t arrive there on time,either.
either side of the river
each side of the river\every side of the pond
both sides of the river
each of us\every one of us
二、句型：
1) Have you ever been to …?
2) I study by working with my classmates.
3) I used to be afraid of the dark.
Did you use to play the piano?
I didn’t use to like tests.
4）It’s fun(nice,good,best…)to do sth.
5) How do you study for a test?I study by listening to the tapes.
6) Teenagers should be allowed to choose their own clothes.
7) I like music that I can dance to.
8) I prefer music that has great lyrics.
prefer to…rather than…与prefer…to…的区别：
prefer to…rather than…后用动词原形
prefer…to…用动名词或名词。

I prefer English to Japanese.（与日语相比我更喜欢英语）
I prefer to learn English rather than learn Japanese.
（与学日语相比我更喜欢学英语）
9) He likes musicians who play different kinds of music.
10) I like places where the weather is always warm.
11) Being a volunteer is great.
12）I go to sleep with my bedroom light on .
三、词组：
on board end up wake up all year aroud make mistakes later on
laugh at take notes look up make up deal with be angry with go by try one’s best beak off be interested in be terrified of go to sleep
in the end make a decision to one’s surprise no longer(not…any more) take pride in pay attention to give up instead of stay up concentrate on at present in the way care about on display to be honest be bad for
stay away from be in agreement take it easy in general as soon as possible
(as soon as one can\could) be willing to quite a few dream of hold on to come true clean up put off set up think up take after fix up
give away put up ask for hand out work out at once clean out
get back to sb be off so far go for walks (go for a walk) thanks to
look forward remind…of… be serious about
五、任务训练:1)Talk about past experences
2)Talk about how to study.
3)Talk about what you used to be like.
4)Talk about what you are allowed to do (Agree and disagree).
5)Express preferences.
6)Talk about places you would like to visit.
7)Offer help.
8)Talk about recent events.
宾语从句：
时态：
1）主句的谓语是一般现在时、一般将来时、现在完成时，从句则用现在某一时态, 甚至可以用过去时
2）主句的谓语是一般过去时，从句则用过去相对应的时态，客观真理、自然现象时仍然用现在时。

语序：如果从句是疑问句，要把疑问语序变为陈述语序。

连词：陈述句——that
一般疑问句——if whether
特殊疑问句——when where who what which how…
*将think, believe, suppose, expect, fancy, imagine等动词后面宾语从句的否定词转移到主句中，即主句的谓语动词用否定式，而从句的谓语动词用肯定式。

I don't think I know you.我想我并不认识你。

I don' t believe he will come.我相信他不回来。

教师可掌握新二出现的知识：
用whether不用if的情况:
1）在介词后面：
We didn’t care about whether it would rain the next day.
2）whether+动词不定式
She can’t decide whether to get married or wait.
They asked me whether to start at once.
3）当与or not连用或提出两者选择时
To tell whether you’d like to go shopping or stay at home.
I don’t know whether he was watching TV or not.
状语从句：
在复合句中作状语,其位置可以在主句前或主句后。

状语从句可以分为时间、地点、原因、目的、结果、比较、让步、条件等几种。

状语从句由从属连接词引导。

1、时间状语从句：通常由when ,as ,while, after, before, since, as soon
as , , till (until), whenever 等引导。

时间状语从句一般放在句首或句
尾.
When you finish the work, you may go out to play with Sam.
I won’t leave until Mum comes back. （till）
My mother was cooking when I got home yesterday.
While my mother was cooking I got home yesterday.
They were running quickly across the road when(at that time) they heard the sound of a truck coming.
As we waited the bus , we sang songs loudly.
2、地点状语从句：通常由where, wherever等引导。

Go back where you came from!
I will never forget to catch the thief who stole my necklace
wherever he may be.
3、原因状语从句：通常由because, since, as等引导,一般放在句首或句尾。

如：He went abroad because his father had found a good university
for him.
Because since as-----for的区别:
He is not at school today because he is seriously ill.
As all of you have got here,now, let’s go to the zoo.
I will ask Lin Tao to go with me since you are very busy.
We must be off now for the match starts at 7：00.
4、目的状语从句通常由so that..., so...that..., in order that... 等引导,往往
放在句尾,从句中通常含有can / could / may / might等情态动词。

He got up earlier so that he could catch the first train.
(与so as to,in order to,to 的转换)
5、结果状语从句:通常由so that..., so...that...等引导,放在句尾。

结果状
语从句一般表示已经发生的事情,故多为过去时态。

He lost so many bikes that he decided never to buy a new one.
（与such…that…以及too…to…,enough to…的转换）
6、比较状语从句(前面已讲过)
7、让步状语从句:通常由though (although), as, even if( even though), however,
whatever等引导。

Even if you pay the debt for me, I will not thank you because it has nothing to do with me.
He wears a T-shirt though it is very cold.
8、条件状语从句:通常由if, unless, as long as等引导,条件状语从句一般放在句
首或句尾.
If it doesn’ t rain tomorrow，we shall go hiking.
If you don’t work hard，you’ll fail (in )the eaxm.
You ‘ll fail( in )the eaxm unless you work hard.
If you work hard，you’ll pass the eaxm.
Work hard,and\then you’ll pass the eaxm.
If there were no air(Without air),there would be no living things.
[注意] 1、because与so；(al)though与but(在句中可加still或yet连用), if与so 不可以同在一个句子中成对出现。

2、时间、条件、原因,让步状语从句放在句首时需要用逗号与主句隔开。