常用词汇和短语

1、常用词汇和短语辨析1.about;around; round做副词时都含有“四处”、“遍地”的意思。about系常用词，如：look about 四处看。around具有about的基本意思，因此look about=look around。但在下列短语里around没有about正式，如：travel around 各处旅行。round和around在非正式用法中可以互换，但一般用round时更简练。在正式用于中，一般用round指“旋转”，而用around指“处处”，“到处”。l另外，英国人用round的地方，美国人倾向于用around,如：Winter comes round. (BE.

2、)lWinter comes around. (AE.)l即学即练l用around, round和about填空：l1.She turned_ at such a noise.l2.I have been looking for it all _.l3.They looked_, but saw nothing.round/aroundaroundabout/aroundl2.above all; after all; at all; in alllabove all意为“尤其是”、“首先”、“最重要的是”，常位于句首或句中，做插入语，起强调作用。lafter all意为“毕竟”、“终究”、“

3、终归”、“到底”，在句子位置较灵活。可位于句首、句中或句末。lat all用于否定句时，意为“丝毫；根本”;用于疑问句时，意为“究竟，到底”；用于条件句时，常译为“当真，实在”。用于肯定句中，表示说话人的某种情绪或情感（如怀疑或惊奇等），意为“竟然”等。in all意为“总共，共计”。l1.A clock must_ keeps good time.l2._,your birthday is only two weeks away.l3.He is,_, a small child.l4. He doesnt like you_.l5.I was surprised at his coming

4、_.l6.There are 50 students _in our class.above allAfter allafter allat allat allin alll3.add; add to; addto; add up toladd作“加，增加”解时，既可作及物动词，又可用作不及物动词；作“又说，补充说”解时，与直接或间接引语连用。ladd to意为“增添，增加，增进”。laddto意为“把加到”,是把前一项加到后一项之后或之中。ladd up to意为“加起来总共是/累计得”，该短语不用于被动语态。即学即练1.If the tea is too strong,_ some mor

5、e hot water.2.After a short while, he_ that he would try his best.3. The bad weather _our difficulties.4._two to seven, and you will get nine.5. All his school education _no more than one year.addaddedadded toAddadded up to4.affair; thing; matter; businessaffair 意为“事情、事件”，含义较广，泛指已做或待做的事；复数affairs一般指

6、商业事务及政府的日常事务，如财政管理、外交事务等。thing 意为“事情、事物”，不管大事小事、好事坏事均称为thing,一般不能专指事务；复数things还可做“形势” 解。matter侧重指须留心的要事或问题、难题。lbusiness作“事务、事情”解时，一般不能用复数，常常指所指派的任务、责任；有时说的是指派的工作或商业上的买卖活动。l即学即练1.I wanted the celebration to be a simple family_.2. Word/international/business_.3. Its a _ of time before they bring out t

7、heir own products.4. Lets get down to _at once-well stop to have a rest.affairaffairsmatterbusiness5. a great deal; a great deal ofa great deal 既可用作名词，意为“大量，许多”,做主语、宾语；又可以用作副词，意为“很”或“非常”，做状语，修饰动词或用来强调比较级。a great deal of意为“大量的”，“非常多的”，相当于much, 作定语，后接不可数名词。即学即练1._has been studied and this is the best

8、way.2.We are _cleverer than before.3. _time/money/energy has been spent on the project.A great deala great dealA great deal of6. agree on; agree to; agree with; agree thatagree on 作“就取得一致意见”解。agree to有两层含义和用法：其一是to作为动词不定式符号，其后跟动词原形，作“同意（答应）做某事”解。其二是to作为介词，之后跟表示“计划/条件/建议”等一类的名词或代词。lagree with作“同意某人的意

9、见”解，其后可跟表示人的名词或代词，也可跟表示“意见”或“说的话”的名词或从句。lagree that作“认为”解，其后跟宾语从句。l即学即练1. We _ what he said at the meeting.2.The building of a new car factory was _ last month.agreed withagreed onl3. I _ your composition is very good.l4. My father _buy a new pen for me.l5. They have _ our plan?l6. He _ my opinions.

10、agreed thatagreed toagreed toagreed with7. allow; permit; letl三者均可作“允许”解，但各有侧重：allow和permit在许多情况下可以通用，但permit较allow正式，含有“积极地、从正面允许”的意义。Allow重在“允许”或“容许”，偏重默许，也可表示客气的请求。注：allow和permit常用于allow/permit sb. to do sth.或 allow/permit doing sth.结构中。let 作“允许”或“让”解，主要用于口语，一般可与allow互换。作“允许”解时，常暗含“听任”、“默许”之意；作“让

11、”解时，常含“祈使”或“建议”之意。注意：let之后作宾补的不定式不带to,且不可用于被动语态，而allow则相反。即学即练l1.Dogs are not _ in the parks in Beijing.l2.The rules of the club do not _lSmoking.l3.He _me to take his dictionary.l4. Will you _me to use your bike?l5. Please_ me walk with you.l(= Please _me to walk with you.)permittedpermitallowedall

12、owletallow8.although; though; as三者均可表示“尽管；虽然”，引导让步状语从句。although用法较正式，语气较强；though较常用； as则主要用于倒装句。它们的用法有如下几点值得注意：状语从句由although, though或as引导，主句之前不可有but, and, so, however等并列连词，但可有yet或still等副词。although与though常可互换。 as表示“尽管；虽然”，只能用于倒装句，即：将表语、状语或谓语动词放在as之前。注意：如果表语是单数名词，要省略a。though也可这么用。though可以放在句末，表示“但是，然而

13、”，although却不能。lalthough只能来陈述“事实”，不能表示“假设”。l因此可以说even though“即使”、as thoughl“好像=as if”,不能说even although或 as although。l即学即练l1. I believe you are on dutyeven _ youre in plain clothes.l2. _he believes it, yet he will not act.thoughAlthough/Thoughl3. Young _ he is, he knows a lot.l4. Child _he is, he can

14、speak two foreign languages.l5. They said they would come; they did not,_.as/thoughas/thoughthough10. eager; anxious; curiouseager意为“渴望的”，指有进取精神，急于求成的亢奋情绪或不耐烦心理。常构成短语：be eager for sth.(= be anxious for sth.)渴望某物，急切想要某物； be eager to do sth.(=be anxious to do sth.)渴望做某事anxious着重指失望或不能得到所希望的东西而感到不安。常用于

15、以下短语：be anxious for sth. 渴望某物be anxious to do sth.渴望去做某事be anxious about sth.为而担忧lbe anxious for sb. to do sth.渴望某人做某事lcurious意为“好奇”，常用短语：be curious about sth.对好奇l即学即练l1.My mother often gets a bit _ if we dont arrive when we say we will.l2.Little Tom was _about robot when he visited the Science Muse

16、um.l3. I was _to see my sister as soon as she got to the airport.anxiouscuriouseager/anxious11.argue; debate; dispute都含“辩论”的意思。argue着重“说理”，“论证”和“企图说服”。debate着重“双方各述己见”，内含“交锋”之意。dispute指“激烈争辩”，含有“相持不下”或“未得解决”之意。即学即练1.I _ with her for a long time, but she refused to listen to my reason.2.We have been

17、_about the issue.3.Whether he will be elected as chairman is still_.argueddebatingdisputed12.argue;quarrel; discuss这三个动词均有“争”的意思，但“争”法不同。argue着重就自己的看法或观点，提出论证，同他人“争论”或“辩论”。argue同with搭配，其后接人；与about连用，其后接事物。quarrel是指对某事不喜欢或强烈不满而发生的“争吵”或“吵架”。同with搭配，其后接某人；和about连用，其后接某事。discuss是指认真交换自己的意见或看法的“讨论”。即学即练1

18、.We_ with them about this problem for a long time.2. He often _about their housework with his wife.3.Well _the use of the articles tomorrow.arguedquarrelsdiscuss13. as(so) far as; as(so) long aslas(so) far as的意思是“就而言（所知）”，as(so) far as sth. Is concerned是其中一种具体用法，意为“就某事而言”。las(so) long as 意为“只要”，引导条件

19、状语从句。即学即练1._ I know, more than 10 million laid-off workers have found their new jobs.2. There is nothing that we cant do _we keep on trying to do it.3. _the tourism of China is concerned, there is a long way to go.As far asso/as long asAs far as14. asleep; sleeping二者都是形容词。asleep仅用作表语，不能作定语，表示“睡着，熟睡”

20、的意思。sleeping一般只能用作定语，放在名词前，表示“睡眠中的，休止的”意思。如：我们不能说： an asleep baby,但可以说：a sleeping baby(一个熟睡的婴儿)。a sleeping dog正在熟睡的狗sleeping car卧车； sleeping bag 睡袋l1. He was _with his head on his arms. (他头枕着手臂在熟睡。)l2.She bought her baby a _ bag.即学即练asleepsleeping15. as though; even though; thoughlas though（=as if）意

21、为“好像；似乎”，引导方式状语从句或表语从句。如：lHe spoke as though (as if) he had been here before.他说话的口气好像以前来过这里。leven though（=even if）,意为“即使”，引导让步状语从句。though也可引导让步状语从句，意为“虽然”；even though有退一步设想的意味，与though不同。though引导的句子所说的是事实，even though引导的句子所说的则不一定是事实。即学即练l将下面的句子译成汉语l1. It looks as if (as though) it is going to rain.l2.

22、He will not tell the secret even thoughl(even if) he knows it.l3. He will not tell the secret though he knows it.看起来好像要下雨。即使他知道这个秘密，他也不肯说出来。他虽然知道这个秘密，但他不会说出来。16. at the beginning; in the beginninglat the beginning在初；在开始的时候，常与of连用。lStudents usually have a study plan at the beginning of term.lin the b

23、eginning相当于at first,表示“起初、开始”时，含“起初是这种情况，而后来却不是这种情况”之意，不与of连用。lIn the beginning, some of us took no interest in physics.即学即练1.He told his own story in New York_ the meeting.2._, some Chinese students are not interested in learning English.at the beginning ofIn the beginning17. at the age of; by the

24、age ofat the age of 表示“在岁时”，后面接基数词，强调某一时刻的情况或动作，用于一般过去时，作时间状语。At the age of six, he began to learn English.by the age of表示“到岁的时候”、“在岁以前”，后面接基数词，强调到某一时刻为止的结果，用于过去完成时或将来完成时，做时间状语。By the age of sixteen, he had learned to drive a car.即学即练l1. She learned to play the piano _lten.l2. You will have learned

25、more than 2,000 English words _fourteen.at the age ofby the age of18.at the time; at that time; at one time; at a timelat the time通常用于过去时句子中，指某件事情发生的“当时”、“那时”。lMany people saw the strange thing happen at the time.l当时，许多人都看到了这件奇怪的事情的发生。l有时，at the time的后面可接 “of”短语。这时，它表示“在（某事态）发生的时候”或“在的时代”。lIt happen

26、ed at the time of King Alfred.l事情发生在阿尔弗雷德国王时期。lat that time则通常指前文明确提到的某个时期、时候。lat one time=during a period of time in the past “过去有一段时期”，“曾经”。lThey used to be good friends at one time.lat a time则意为“一次”，表示一个时间单位。它常与表示数量的词语连用，表示频率。lTake the medicine three times a day and three pieces at a time.即学即练l1.

27、 Were you in San Francisco_ of the big earthquake?l2.In the 17th century much corn was grown in Tibet and Sichuan. _ the land along the Changjiang River was becoming very crowded.l3. Dont speak all at once. One _, please.l4. There used to be an old church in the small village_.at the timeAt that tim

28、eat a timeat one time19. atspeed; withspeedlat the speed of 或者atspeed, 意为“以的速度”。l而当speed被all, lightning,great等修饰时，介词应用with。我们可用一句话口诀来帮助记忆：l都（all）以闪电般（lightning）大（great）的速度行驶。即学即练l1. Our car was running _all speed on the expressway. 2. The Long March No. 2 Rocket sent up the satellite into space _ th

29、e speed of 11.2 kilometers per second.withat20. as; because; since; forl这四个词都是表示原因或理由的连接词，但是as, because, since是从属连词，引导原因状语从句，for是并列连词，所引导的不是原因状语从句，而是表示理由的对等句子，是对前面所讲内容补充和说明。在语气上由强至弱依次为because since as for。lbecause引导的从句多置于句末，表示直接的原因或理由，表示产生那种结果的必然的因果关系，在回答why的提问时，必须用because作答。las 与since引导的从句多置于句首，不过a

30、s表示十分明显的原因，只说明一般的因果关系，可译为“因为、由于”；而since则表示稍加分析、对方已知的原因，一般可译为“既然”。For引导的从句一般放在句末，其前用逗号，它所叙述的理由是间接的，即推测性理由，或是对前面叙述的事实或看法的补充说明。即学即练l1. We stayed at home _ it rained.l2. _everyone is here, lets start.l3. _ he was not feeling well, I decided to go there alone.l4. There must be nobody in the classroom,l_

31、the light is off.becauseSinceAsfor21. believe; believe inlbelieve作及物动词时，其后可跟名词，表示“相信”；后接从句或复合宾语时，表示“认为；料想；相信”等。lI believe what he says. 我相信他的话。lbelieve in 是一个动介型短语动词，表示“信奉；信仰”（指对某种思想、主张、观念、行动具有信心）和“信任（have trust in）”。lbelieve 和believe in后均可接表示人的名词或代词，但含义不同。lI believe in him. (I think he is a trustwo

32、rthy man.)lI believe him. (I believe what he says.)l即学即练l1. I _that he will succeed.l2. I _ having plenty of exercise.l3. They _ God.believebelieve inbelieve in22. belief; faith; trust; confidencel都含有“相信”的意思。lbelief指“承认某事是真的，尽管有或没有确凿的证据”，如：belief in ghost lfaith 指 “认为有确凿证据或道理而完全相信”，如：I have faith in

33、 his ability to succeed.l我相信他有成功的能力。ltrust指 “信赖、信任”，含有“坚定的信念”的意思，如： enjoy the trust of the peoplel得到人民的信任lconfidence 指“在有证据的基础上相信”，也常指“自信”、“有把握”，如： She has greatlconfidence in her success.l即学即练l1. He has a _ in God.l2.She has great _ in me, so I wont let her down.l3.Joyce is interested in computers,

34、 so he has _in computer examination.l4.I _ Mark, so I lent him some money.belieffaithconfidencetrusted23.besides; except; but; except for; apart from; as well as; along with; other thanlbesides, apart from, as well as 和along with用于肯定句中时，意为“除外（还有）”。lexcept/but意为“除外（不再有）”；lAll of them have seen the fi

35、lm except/but Wu Dong.l除了吴东外，他们都看过那部影片。lAll of them have seen the film besides/apart from/ as well as/ along with Wu Dong.l除了吴东看过那部影片外，他们也都看过了。lexcept后接名词、代词、-ing或不定式时，可以与but互换；except后接副词、介词短语时，一般不能为but所替换。lIll do everything except/but cook.lThis window is never opened except in summer.除了在夏天，这个窗子从不打

36、开。lexcept for 表示“除了某一点”，排除的不是同类人或物；而except排除的是同类的人或物。lToms quite good-looking except his nose.l汤姆除了鼻子外，哪点儿都好看。lWe all have already been to Beijing except Meimei.l除了梅梅外，我们都已经去过北京。lother than一般用于否定句，表示“除了外（不再有）”。lHe has no close friends other than Jack.l除了杰克外，他没有别的知心朋友。l用在否定句中， but, except, besides和ot

37、her than一般可以互换。lThere arent any other people to do the work except/but/besides/ other than you.即学即练l1. I have learnt two other foreign languages _French.l2.We all took part in the party _ Tom lbecause he was ill then.l3. He has no choice _lto study hard.l4. There is nothing in the room _l_a large ta

38、ble.besides/apart from/as well as/along withexceptbut/except/other thanbesides/butexcept/ other than24.be anxious to; be anxious for; be anxious about; be anxious thatlbe anxious to do sth. 急于/渴望做某事lbe anxious for +名词/代词，强调渴望得到某物或渴望了解某事；后接sb. to do sth.时，表示“渴望某人能做某事”。lbe anxious about 对感到不安/担心/忧虑lbe

39、 anxious that+从句（从句的谓语动词须用虚拟语气）。即学即练l1. I _the result of the examination.l2. We _know the result of the examination.l3.We_Mr. Liu to help us with our English.l4. Mr. Li _ a new car.l5.They _ arrive home before dark.l6.We_she could do her best.am anxious about/forare anxious toare anxious foris anxio

40、us forare anxious toare anxious that25.be known as/for/ to/inlbe known as +身份/职业 “作为而著名”lLiu Huan is known as a singer.lbe known for+特点/特长 “因而著名”lMr. Geldof is well-known for organizing two big pop concerts on the same day.lbe known to其后接表示人的词语，“为所了解/知道”。“（人们都）知道”，其后接动词原形。lHe was known to have inven

41、ted many things.l=It was known that he had invented many things.lbe known in 在某地很著名lHe is well-known in the town where he was born.即学即练1.Were sure youll _an artist.2.Guilin _her beautiful mountains and rivers.3. He_ all in our village at the moment.4.Lu Xun _ Shaoxing of Zhejiang province.be well-kn

42、own asis known foris known tois known in26.be made of/in/from/ by /up oflbe made of指从原材料到制成品，只发生了形状变化，没有发生本质变化（属物理变化）。lbe made from,指从原材料到制成品，发生了质的变化，已无法复原（属化学变化）。lbe made in +时间/地点, “某物何时制造的、某地生产某物”。lbe made by+动作的执行者 “由制成”lbe made up of“由构成/组成”,强调主语由两部分或两个以上的部分构成或组成。即学即练l1.This bike _ Tianjin.l2.

43、This table _wood.l3. The car _1999.l4. Paper _ wood.l5. The kite _ my mother.l6. The team _ten members.was made inis made ofwas made inis made fromwas made byis made up of27.be used for/ as/ bylbe used for表示“被用作”或“被用来做”,后面接名词或v.-ing,其中for表示目的。lbe used as表示“作为而用”或“用作”,l后面接名词或动词不定式，强调使用的工具及手段。be used

44、by表示“由使用”，后面接指人的名词或代词，强调使用者。即学即练l1. A telephone _betterlcommunication(交流).l2.The motorbike_ Liu Ming.l3. A ruler _ often _a knife by him to cut a piece of paper open.is used foris used byisused as28. be pleased with sb.be pleased at/about sth./doing sth./ to do lbe pleased with sb. 对满意；喜欢lbe pleased

45、 at/about sth./doing sth l对（看到或听到的）事感到高兴lbe pleased to do sth. 很高兴或很乐意做某事即学即练l1. The manager_ you before.l2.My boss must _see you again in Hong Kong.l3.I _seeing so many students present.l4. I hear Mr. Zhao _your article.lwas pleased withbe pleased toam pleased at/aboutis pleased at/ about29.be to d

46、o sth.; be about to do sth.;be going to do sth.lbe to do sth. 表示按计划或安排即将发生的动作，后可跟时间状语。lYoure to hand in your papers by 10 oclock.l十点钟以前你得交上试卷。lbe about to do sth.表示打算或安排即将发生的动作，它通常不与时间状语连用。lI was about to go out when someone knocked at the door.lBe going to do sth.有三层含义：l1）表示打算、计划或决定要做某事。lWere going

47、 to spend our holidays in Wales this year.l2)用以表示某事物即将发生或很可能发生。lIm going to be twenty next month.l3）有迹象表明即将发生的动作或状态。lLook at those black clouds, there is going to be a storm.即学即练l将下列句子译成英语。l1.天黑之前我必须到达目的地。（be to do）l2.我正要去上班，这时电话铃响了。（be about to do）l3.明年我们将完成这项工程。（be going to do）I was to reach the d

48、estination before darkness.I was about to go to work when the telephone rang.We are going to complete the project next year.30.beat; strike; hitlstrike通常表示“打一下、打若干下”，不一定都是有意的；还有“打动，使着迷，某种想法突然闪现在脑海里”的含义；也可指“打、擦出（火），（蛇、兽）抓，或（钟）敲响”。lhit指“打中”或“对准来打”，“敲打或打击对方的某一点”。lbeat 着重“连续地打击”。如：殴打或体罚；也指在游戏、竞赛或战争中击败对方

49、；也指“心跳”。即学即练1.I could always _my brother at chess.2. He is still alive-I can feel his heart _.3.She _him playfully over the head with newspaper.4. We were _ by the generosity of even the poorest citizens.5. A snowball _ him on the back of the head.beatbeatinghitstruckstruck31.blame;scold; accuselbla

50、me“责备；责怪”，指某人应对自己不好的行为负责（常与for连用）,或将某件不好的事情归咎于他人（常与on或uopn连用），往往含有把自己当作评判人来评判某事，没有用言语来进行责骂的意思。例如：lHe blamed Tom for the failure.lscold “责骂”，指唠唠叨叨地数说某人，多用于上级对下级、长辈对晚辈的“责骂”。例如：lI hate to scold , son, but you mustnt stay out so late at night.Accuse “责备，谴责，控告”，语气较重，常用结构为accuse sb. of (doing) sth. 谴责某人做了

51、某事或控告某人做了某事Are you accusing me of lying to the boss?你在谴责我对老板撒谎吗？即学即练1.Dont _ it on him, but on me.2.Dont _ the child. Its not his fault.3.Tom _me of stealing his computer when he was out.4. The vase was broken while I was away, so I dont know who to _.blamescoldaccusedblame32.blow down; blow in; blo

52、w off; blow overblow down 表示“吹到”、“刮倒”。blow in 表示“吹进”、“吹入”。blow off表示“吹掉”、“炸掉”、“发泄”。blow over表示“暴风雨吹散”、“过去”、“结束”。即学即练l1. The high winds yesterday _lthousands of trees.l2.We sometimes had quarrels, but they soon _.l3. I had my hat _.l4. A lot of dust _. You must clear it away.blew downblew overblown o

53、ffhas blown in33.break up/down/out/into/in/away/throughbreak up表示“打碎”、“变坏”、“分解”、“终止”、“破裂”。break down表示“瓦解”、“分解”、“失败”、“出故障”、“破坏”、“拆毁”。break out表示“爆发”、“突然发生”。break into表示“强行进入”、“闯入”、“破门而入”、“打断（谈话、讨论）”、“突然来”。lbreak in表示“闯入”、“打断”、“插嘴”，其中in是副词。lbreak away表示“脱逃”、“脱离”、“突然离开”、“隔出”、“戒除”，常与from连用。lbreak throu

54、gh表示“战胜”、“突围”、“穿过而出现”、“突破”。即学即练1.He said his computer_.2.Those old cars will be _for scrap(废铁).3. Last night somebody _ Mr. Browns house and took away many things.4.A fire _after we had gone home.5. The boy often _while his parents are speaking.had broken downbroken upbroken intobroke outbreaks in即学

55、即练6. You must _from bad habits.7. After the heavy rain the sun _The clouds.8. A thief _ and stole a lot of things last night.9. Tom _ the motor bike which he bought five years ago.10. The ice began to _ on the river.break awaybroke throughbroke inbroke downbreak up34. bring on/in/out/down/back/upbri

56、ng on使发生；引起；端上（饭菜）。Tom often brings on meals and his brother, Jim picks up the dishes after meals.The sudden cold weather brought on his cold again.bring in表示“把引进来”、“赚入”、“获利”、“把拿进来”、“吸收”。His new business brings in 1000 dollars.We also brought in some words from English.bring out取出；说出；阐明；出版He brought

57、 out his gun and pointed at me.Bring out the meaning more clearly.They have brought out a set of childrens books.bring back 表示“使回想起”、“归还”、“带回来”。bring down表示“使倒下”、“减少”、“降低（价格、温度）”。bring up表示“呕吐出”、“养育”。即学即练1.Her singing _ memories of my mother.2. They also _some words from their own languages.3. The w

58、ind _a number of trees.4. He _all he had eaten.5.Can you try to get them to _the price?6.All library books must be _before June 25.7.Mr. White _ $500 a week.8.You must manage to _ the temperature.brings backbrought inbrought downbrought upbring downbrought backis bringing inbring down35.broad; wide

59、两者都表示两边或两点之间的距离；都有“宽的”之意。broad着重某物覆盖的范围（如肩、背、胸等的宽），还可表示“宽宏大量”，“广博的，丰富的”。wide着重指边沿间相隔的距离大。另外，wide还表示（人、物、形式等）“广泛的，广阔的，范围广的”。Looking at the new-type camera, the young man with broad shoulders was surprised with his mouth wide open.即学即练1.She has a very _range of interests.2.We went along a _ carpeted p

60、assage.3.There is _gap between the developed countries and the developing ones.4. Her eyes grew _ in surprise at the exciting news.broadbroadwidewide36. but; however这两个连词都有“但是，可是，然而”之意。but连接两个分句或有关部分，表示转折或逻辑上的对比关系，使用最广，口语中更为常见。We love peace but we are not afraid of war.however转折意为比but弱，连接的两个分句或有关部分的