8下语法知识总结
Unit 1 Past and Present
1、现在完成时的肯定句、否定句的构成（以实义动词work为例）
肯定句：I/We/You/They have (I/We/You/They’ve) worked.
否定句：I/We/You/They have not (I/We/You/They haven’t) worked.
肯定句：He/She/ It has(He’s/She’s/It’s) worked.
否定句：He/She/It has not(hasn’t) worked.
2、现在完成时的一般疑问句及其简略答语（肯定、否定）的构成
一般疑问句：Have I/we/you/they worked?
肯定简略答语：Yes, I/we/you/they have.
否定简略答语：No, I/we/you/they have not(haven’t).
一般疑问句：Has he/she/ it worked?
肯定简略答语：Yes, he/ she/it has.
否定简略答语：No, he/she/it has not (hasn’t).
3、现在完成时的用法
用法1：过去开始发生的动作或存在的状况一直延续到现在
例句：They have waited for more than two hours.他们等了两个多小时。
He has been an English teacher since 2002.自从2002年以来他一直当英语教师。
特别提示：常用的标志词有：for t wo days/ weeks…, for a long time, since last year/ 2005…
用法2：表示过去已经完成的动作对现在造成的影响
例句：I’ve alread y mailed the letter.那封信我已经寄出。
Have you ever eaten French cheese? 你（曾经）吃过法国奶酪吗？
Has it stopped raining yet? 雨已经停了吗？（yet表示期待雨停止）
I have just finished my homework. 我刚做完家庭作业。
特别提示：常用标志词有：already(用于肯定句),never(用于否定句)，ever(用于疑
问句，问初次经历)，yet(用于否定句、疑问句)，just(位于实义动词前)，before （一般位于句末）
用法3：过去发生的动作，到现在为止这一时间段中，多次动作的总和或所做工作量的积累
例句：She really loves that film. She has seen it eight times.她真的很喜欢那部电影。她已看了八遍了。（多次动作的总和）
We have learned three English songs this term.这学期我们已经学了三首英语歌曲了。（所做工作量的积累）
4、现在完成时的时间副词和时间短语:
1)副词already和yet。already一般用于肯定句中，yet一般用于否定句和疑问句中。
e.g. We have finished our homework.
2)副词ever 和never。多用于否定或疑问句中，表示“曾经”或“从未“等。
e.g. Have you ever been to the Great Wall? 你曾经去过长城吗?
3)用just表示到说话时为止的时间状语,
e.g. I have just seen her, but I don’t know wh ere she is now .
注意：当在肯定陈述句中含有already或just 时，在转换成否定句或疑问句时，要把句中的already 或just 去掉，在句末加上yet.
Unit 2 Travelling
1.have/has been 和have/ has gone 的用法
have/has been（to）、gone（to）、been （in）三者之间的根本区别：
have/has been to 表示当事人曾经去过某地
have/has been in 强调当事人在某地待过一段时间
have/has gone to 强调说话时当事人不在现场，去了某地
注意用法：been (to) + 地点+次数been (in) + 地点+ 段时间/句子
2.和for 或since 连词的动词
现在完成时态表示过去发生的动作或存在的状态, 一直持续到现在, 也许还将继续下去, 可以和表示从过去某一时刻延续到现在的一段时间的状语连用, 即for + 一段时间, since + 时间点/ 从句, in the past ten years等, 谓语只能用延续性动词. 注意：
1）动词必须是延续性/持续性动词
---动作具有延续性.e.g. work, wait, study, know learn, copy, talk, lie, have, visit.
2）动词是短暂性动词,必须把它改为延续性动词或延续性的状态.
come, go, arrive, get to, return------be in / at
die---be dead ; open (v.) ----be open (adj.) close--- be closed
join---- be in/ be a member of…be a … member; be in, be with
buy--- have borrow----- keep
get up----be up wake up----be awake
fall asleep/get to sleep---- be asleep
leave--- be away ; leave s.w.----be away from s.w
catch //get// take a cold --- have a cold
become ----be finish ---- be over;
begin // start --- be on begin to do---- do
move to ----live in end---be over
turn on //off----sth. be on//off
return, come, back, get back, go back ---be back
hear from, get ( receive) a letter from --- Have a letter from
get, turn, become (变得，成为)作系动词---be
get married---be married
Unit 3 Online tour
一般过去时和现在完成时的区别：
1、一般过去时和现在完成时都可以表示过去发生的动作，但是在具体语境中，这两种时态有明显区别。
2、一般过去时表示过去某个时刻发生的动作或存在的状态。
如：I went to Beijing last month. 我上个月去北京的。
Tom was in China in 2008. 2008年汤姆在中国。
3、现在完成时表示过去的动作持续到现在或对现在产生影响。
Mr. Lin has taught in this school since he graduated from college.
The kitchen is very clean. Who has cleaned it?
注意：（1）一般过去时常与过去点时间连用。如：yesterday, last week, two years ago,just now, in 2008，the other day, when he was born等。
（2）现在完成时通常和一些副词或一段时间状语连用。如：ever, never, just, already, yet, many times, before, these days, recently, so far, over/in/during the last/ past few years, since…, for…等。
(3)现在完成时与段时间状语搭配时要注意短暂性动词转化成持续性动词。
I have kept this book for a week.
My father has been in Beijing since two days ago.
(4) 常见的短暂性动词与持续性动词的转化：
buy→have had, borr ow→have kept, open→have been open, close→have been closed, begin/start→have been on, finish/end→have been over, go/ come to sp.→ have been in sp., get to/reach/arrive at sp. → have been in sp., catch a cold/virus→ have had a cold/virus, marry sb./get married to sb. →have been married to sb. leave→have been away (from sp.), fall asleep→have been asleep, wake up→have been awake, begin/start to do sth. →have done sth.
Unit 4 A good read
一、”疑问词+动词不定式”结构作动词的宾语.
(1)疑问词包括疑问代词what,which,who和疑问副词how,when,where等.常和此结构连用的动词有：know, learn, see, hear, ask, advise, decide,explain, forget, remember, think, understand, wonder等
(2)有些动词,如advise, ask, show, teach, tell等,其后可以接双宾语.
Please tell me how to get there.
(3)有些疑问词,如what,which,whose,how many, how much等,其后可以先接一个名词,再接动词不定式.
She wondered how many subjects to choose.
(4)在此结构前,有时也可以是如sure,clear等的形容词.
I am not sure which way to take.
(5)此结构在句子中还可以作主语和表语.
The problem is when to leave the place.
(6)此结构可以改写成由该疑问词引导的从句.
I don’t know what to do.= I don’t know what I should do.
注意: 所有疑问句中,why不能与动词不定式连用.
二、must/have to的用法
must表示主观的义务和必要,主要用于肯定句和疑问句,意思是“必须,得,要”.
must的否定式must not表示禁止,意思是”不能,不许”.
must还可以表示肯定猜测,意思是”一定”.
have to 表示一种客观的需求，意思是不得不. have to 有人称和数的变化. have to的否定式是don’t have to.
Unit 5 Good manners
enough的用法
⑴你年龄足够大了可以了解礼仪了。You are old enough to learn about manners. Enough+noun./adj./adv.+enough
⑵英国人太有礼貌而不会在公共场所大叫。
British people are too polite to shout loudly in public.
…enough to do … 足够…而做某事
too..to do.. 太..而不能做某事
so…that… 如此…以致…
such…that… 如此…以致…
他太小了不能上学。（三种）He is too young to go to school.
=He is not old enoug h to go to school.=He is so young that he can’t go to school.
这个房间太小了十个人住不下。（四种）
The room is too small for ten people to live in.=The room is not old enough for ten people to live in.=The room is so small that ten people can’t live in it.=It’s such a small room that ten people can’t live in it .
Unit6 Sunshine for all
一、It is + adjective + to-infinitive
在该句式中，it是形式主语，真正的主语是不定式短语。这种句式也可用动词不定式或动名词放在句首直接做主语。如：
It is wrong to look down on the disabled people .
=To look /Looking down on the disabled people is wrong .
二、It is + adjective + for…+to-infinitive
在该句型中，it是形式主语，for引出不定式的逻辑主语sb. ；表语形容词只是说明不定式的特征而不表示人的性质或特征；for sb. to do sth.通常被称为动词不定式的复合结构。常用于这种结构的形容词有easy, difficult, important, hard, necessary, possible, interesting, meaningful 等。如：
It is difficult for us to finish the work today .
It is meaningful for people to donate to the charities .
三、It is + adjective + of…+to-infinitive
在该句型中，it是形式主语，of引出不定式的逻辑主语sb. ；表语形容词是表示不定式的主语特征。常用于这种结构的形容词有kind, polite, clever, foolish, silly, good, nice, generous, careful, careless, selfish 等。如：
It is very nice of you to say so .
It is generous of him to share his computer with you .
注意：在上述句式中，第一和第三可以互换，意思不变。如：It is good for students to do morning exercises every day .= It is good that the students do morning exercise every day .
Unit 7 International charities