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1、八年级下英语知识汇总Unit1情态动词should、反身代词一、情态动词Should1.定义：should作情态动词，可以表示责任和义务，意为“应当；应该”，可以用于各种人称。2.用法：肯定句主语+should+动词原形+其他否定句主语+should not/shouldnt+动词原形+其他一般疑问句Should+主语+动词原形+其他？特殊疑问句（以what为例）What should +主语+动词原形？You should listen to your parents.You shouldnt go out last night.Should I take my temperature fi
2、rst?What should I do?3.近义表达：ought to do表示“应该；应当”be supposed to do 表示“应该做某事”You ought to diet and take more exercise.They are supposed to shake hands with the guests.二、反身代词1.定义：反身代词是表示反射或强调的代词，由第一人称、第二人称形容词性物主代词或第三人称代词的宾格形式的词尾加-self或-selves构成。可译为“本人；本身；自己”。2.形式：第一人称第二人称第三人称单数myselfyourselfhimself, he
3、rself, itself复数ourselvesyourselvesthemselvesUnit2用could表达建议、动词不定式一、用could表达建议用could来表达建议的用法，此时could可以翻译为“可以”，could用于表达建议时语气较委婉，在这里的could不是can的过去式。You could write him a letter.You could help to clean the park.二、动词不定式1.定义：动词不定式的基本形式是“to+动词原形”,否定结构是“not to+动词原形”。动词不定式在句中不能作谓语,其形式不随主语的人称、数和时态而变化。2.用法：作主
4、语To learn English well is very important. = It is very important to learn English well. 作表语My job is to look after patients.作宾语We want to go swimming. 作宾语补足语She invited me to go to a concert.作定语He has too many things to do.作状语She got up very early to catch the early bus.3.“疑问词+不定式”结构动词不定式可以用在疑问词what
5、、how、when、where等之后，该结构可作主语、宾语、表语等。作主语：How to get there is a problem.作宾语：I dont know what to say.作表语：The question is how to learn English well.*注意：当“疑问词+不定式”结构作宾语时,通常可以和宾语从句进行同义转换。They are talking about how to get there.= They are talking about how they can get there.4.常用搭配（1）有些动词只能跟动词不定式作宾语。如：plan、h
6、ope、agree、decide等。We plan to go climbing.My father agreed to take us to the museum.They decided to join the swimming club.（2）有些动词后要跟动词不定式作宾语补足语。如：want sb. to do sth.想要某人做某事tell sb. to do sth.告诉某人做某事encourage sb. to do sth.鼓励某人做某事warn sb. to do sth.警告某人做某事ask sb. to do sth.请求某人做某事advise sb. to do sth
7、.建议某人做某事Unit3用could提出请求、征求许可、while的用法一、情态动词Could1.用could提出请求常见的结构是“Could you（please）？”,意为“你能吗?”或“请你好吗?”，是一种比较客气、有礼貌的提出请求的方式。如果同意对方的请求,可以用OK.或No problem.等来回答。如果不同意对方的请求，可以用Sorry, I cant.等来回答,并以委婉的方式来解释原因。-Could you please open the door? -Sure.2.用could征求许可常见的结构是“Could I？”，意为“我能/可以吗?”。此时肯定回答和否定回答都不用cou
8、ld,习惯上肯定回答用may, can等；否定回答用cant或mustnt(语气重)。-Could I smoke here? -No, you cant. Look at the sign “No smoking”!二、while的用法1.while用作连词时，有以下几种含义：释义用法例句当时候引导时间状语从句While I was watching TV, the bell rang.虽然,尽管引导让步状语从句While he is in poor health, he works hard.而,然而连接两个并列分句，表示对比关系I like singing while she likes
9、 dancing.2.while引导状语从句时，需注意：（1）while引导时间状语从句既可放在句首，也可放在句末；而while引导的让步状语从句一般放在句首,不放在句末。另外，也可以从意义上加以区分。时间：Her parents died while she was still at school.让步：While he was tired, he went on working.（2）while引导让步状语从句时，如果从句的主语和主句的主语相同，且谓语含有be动词，那么从句的主语和be动词都可以省略。While he was ill, he went there. (= While ill
10、, he went there. )（3）while引导的时间状语从句，从句中的谓语动词常用延续性动词，表示“与同时，在期间”。While we were talking, the teacher came in.Unit4until so that although 引导的状语从句、why dont you句型一、until、so that、although 引导的状语从句1.定义：状语从句就是在句中作状语的从句。状语从句有好几种，如时间、原因、条件、结果、目的、让步状语从句等。2.类型：（1）until引导的时间状语从句Until意为“直到为止；到时”。注意until和notuntil在用
11、法上的区别。Continue walking in this direction until you see a sign.I didnt wake up until I heard the alarm clock.（2）so that引导的目的状语从句So that意为“为了；以便”，引导目的状语从句。注意so that、in order that、in order to在用法上的区别。Let me take down your telephone number so that I can call you later.（3）although引导的让步状语从句Although意为“尽管；虽然
12、”，常用于引导让步状语从句，且引导的句子常指事实，而不指设想。Although可置于句首（此时多用逗号与主句分开），也可置于句末，也可用于句中表强调。Although my uncle is old, he looks very strong and healthy.二、why dont you？句型 Why dont you do sth.？意为“你为什么不做某事呢？”，与Why not do sth.？是同义表达。Why dont you stay for supper? = Why not stay for supper?*Why not？是常见的口语表达，意为“为什么不呢？”用于表示同
13、意或赞同。Unit5when while 引导的状语从句、过去进行时一、when、while 引导的状语从句 When、while都可以用来引导时间状语从句，它们可以和过去进行时搭配，主句和从句的时态搭配是这样的：主句的时态连词从句的时态过去进行时when一般过去时一般过去时while过去进行时过去进行时while过去进行时When the rainstorm came, he was reading in the library.Someone came in while my mother was cooking.They were cleaning the classroom while
14、 you were playing games.*时间状语从句的引导词有很多,常见的有：when当的时候The army was disbanded（解散）when the war came to an end.while在期间I lived in a hostel while I was a student.before在之前I wiped my shoes on the mat before I came in.after在之后I found your coat after you had left the house.as 当的时候He smiled as he passed.since
15、自从Since his wife died, he has let himself go.until直到Lets wait until he comes back.二、过去进行时1.定义：过去进行时用于描述过去某个时刻正在发生的动作或存在的状态，它的基本结构是“was/were + 动词的现在分词”They were doing their homework at eight oclock yesterday evening.2.用法：肯定句主语+was/were+现在分词+其他否定句主语+was/were+not+现在分词+其他一般疑问句Was/Were+主语+现在分词+其他？肯定答语Yes,主语+was/were.否定答语No，主语+wasnt/werent.My sister was playing with her cat
