中考语法复习

第一部分：词法中考考点 一、名词一、名词的复数：1.名词变复数的规则形式1).一般情况下直接加s book-books cup-cups 2).以辅音字母+y结尾的，先变y为i再加es . city-cities family-families 3).以s、x、sh、ch结尾的加es . bus-buses wish-wishes watch-wathes 4).以o结尾的多数加S 初中阶段只有三个单词加es . tomato-tomatoes potato-potatoes hero-heroes 5).以f、fe 结尾的，先把f、fe变v 再加es . leaf-leaves self-selves shelf-shelves life-lives thief-thieves 2.少数名词的复数形式是不规则的。 man-men woman-women child-children foot-feet tooth-teeth mouse-mice 3.单数和复数形式相同。 deer-deer fish-fish sheep-sheep Chinese -Chinese Japanese-Japanese 4.某国人的复数。1). 中、日不变。Chinese-Chinese Japanese-Japanese2). 英、法变。 Englishman-Englishmen Frenchman-Frenchmen 3). 其余s加后面。 American -Americans German-Germans Australian-Australians二、不可数名词：1.不可数名词：1).不能直接用数字表数量 2).不能直接加a或an 3).没有复数形式 4).可用some、any 、lots of、plenty of 、much 修饰 5).可用“量词短语”表示2.不可数名词的数量的表示方法： a / 数字+ 量词 + of + 不可数名词 a piece of paper a cup of tea a glass of milk 三、名词的所有格：1. s 所有格。1).用and连接两个并列的单数名词表示共有关系时，这时只在最后一个名词后加“s.” This is _(Mary and Lily) bedroom .2). 1).用and连接两个并列的单数名词表示各有关系时，这时分别在每个名词后加“s.” These are _(Tom and Jack ) school bags .3).以s结尾的名词，变所有格时在s后加“”,不以s 结尾的复数名词，仍加“s” Teachers Day Childrens Day 4).表示店铺、医院、诊所、住宅等名称时，常在名词后加 s 代表全称。 at the doctors at the Bobs 5).由some、any、no、every与one、body 结合的复合不定代词something 、anything 等和else 连用时，所有格应加在else的后面。 This is _(somebody else ) pencil .6).表示时间、距离、国家、城市等无生命的名词，也可在词尾加s 来构成所有格。 an hours ride two weeks time Chinas capital 2.of 所有格：1).of 用来表示无生命的名词所有格。 the map of China the door of the room 2).双重所有格： of + 名词所有格 of + 名词性的物住代词 He is a friend of my _(brother ) . Is she a daughter of _(you)?四、名词作句子成分：1.名词作主语1).表示时间、金钱、距离作主语时，谓语动词用单数。 Two hours _(be) enough for us to get there .2).量词短语“数字+量词+ of +”作主语时，谓语动词应与量词保持一致。 A pair of shoes _(be) under the bed . Two pieces of paper _(be) on the desk .3).名词+介词（with、except 、along with .）+名词作主语时，谓语动词应与前面的名词保持一致。 The teacher with the students _(be) planting trees on the hill .4).短语“neithernor、eitheror、not onlybut also ”连接主语时，谓语动词实行就近原则。 Neither he nor I _ (be) a Frenchman .2.名词作定语：1).名词作定语时，一般用单数形式。 There is a shoe factory near the school .2).名词作定语时，个别情况用复数形式。(sport ) The sports meeting will be held next week .3).man、woman 作定语表示性别时，man、woman随后面的名词单复数而变。 one man teacher two women teachers 中考考点二： 冠词的用法 考查重点冠词的考查重点包括不定冠词a和an的用法，定冠词the的用法和零冠词的用法等。一.a和an的区别不定冠词有a和an两种形式，a用于辅音(不是辅音字母)开头的词前，an用于元音(不是元音字母)开头的词前。 例如：a boy, a university, a European country; an hour, an honor, an island, an elephant, an umbrella, an honest man ,a useful book不看字母看读音,不见原因(元音)别施恩(n)二.不定冠词的用法1.泛指某一类人、事或物；相当于any，这是不定冠词a/an的基本用法。 A horst is an animal2.泛指某人或某物，但不具体说明何人或何物。 A girl is waiting for you.3.表示数量，有“一”的意思，但数的概念没有one强烈。 I have a computer.4.表示“每一”，相当于every. I go to school five days a week.我一周上五天课。5.用在序数词前，表示“又一”，“再一”。 I have three books. I want to buy a fourth one.6.用在某些固定词组中：a lot(of), after a while ,a few ,a little ,at a time ,have a swim ,have a cold ,in a hurry ,for a long time,have a good time ,have a look三.定冠词的用法1.特指某(些)人或某(些)物，这是定冠词的基本用法。The book on the desk is mine2.指谈话双方都知道的人或事物。Open the window, please.3.指上文已经提到的人或事物。I have a car. The car is red.4.指世界上独一无二的事物。Which is bigger, the sun or the earth?5.用在序数词，形容词最高级前。The first lesson is the easiest one in this book.6.用在由普通名词构成的专有名词前。the Great Wall 长城，the United States 美国7.用在某些形容词前，表示某一类人。the poor穷人, the blind盲人8用在姓氏复数形式前，表示“全家人”或“夫妻俩”。the Greens 格林一家或格林夫妻俩9.用在方位词前。on the left在左边，in the middle of在中间10.用在乐器名称前。She plays the piano every day.11.用在表示海洋，河流，山脉，群岛及国家和党派等名词前。the Black Sea黑海，the Yangzi River长江12.用在某些固定词组中：all the same仍然；all the time一直；at the moment此刻；at the same time同时；by the way顺便说；do the shopping/washing买东西/洗衣服；in the morning/afternoon/evening 在上午/下午/晚上；in the open air 在户外，在野外四.零冠词的用法1.棋类,球类,一日三餐名词前不用任何冠词 Play chess play football have supper特例：当football，basketball指具体的某个球时，其前可以用冠词：I can see a football.我可以看到一只足球。Wheres the football？那只足球在哪儿？(指足球，并非“球类运动”)2.季节,月份,星期,节假日名词前不用任何冠词.In July in summer on Monday on Teachers Day3.人名,地名,国家名前不加冠词Beijing is the capital of China4.学科,语言,称呼,语职务名词前不用冠词Math is hard to learn5.复数名词表示类别时不加冠词They are workers I like eating apples6.名词前已有物主代词(my，your，his，her等)、指示代词(this/these，that/those)、不定代词(some，any等)及所有格限制时,不用冠词my book(正)；my the book(误)7.在表特定的公园，街道，车站，桥，学校等之前。No.25 Middle School五.用与不用冠词的差异in hospital住院 /in the hospital在医院里 in front of在(外部的)前面 /in the front of在(内部的)前面 at table进餐 /at the table在桌子旁by sea乘船 /by the sea在海边 go to school(church)上学(做礼拜) /go to the school(church)到学校(教堂)去two of us我们当中的两人/the two of us我们两人(共计两人)next year明年 /the next year 第二年a teacher and writer一位教师兼作家(一个人)/a teacher and a writer一位教师和一位作家(两个人)中考专题三：代词一人称代词： 单数复数主格宾格主格宾格第一人称Imeweus第二人称youyouyouyou第三人称it/she/heit/her/himtheythem1.主格作主语,宾格作动词或介词的宾语. He teaches _(we) Chinese .2.三种人称代词并列时,顺序为: 单数:二,三,一 （You, she and I ） 复数:一,二,三 (we , you and they )注:若把责任担,第一人称最当先,(即若做错事时,把第一人称放在最前面.) She and I have been to Beijing . Who broke the window ? I and Mike .注：it 还有一些特别的用法。 1）用作形式主语,常用于 “Its +adj +to do sth”句型中. 2) 用在句型: “It seems that ”中. 3) 用在句型: “Its ones turn to do sth”中. 4) 用在句型: “Its time to do sth / for sth”中. 5) 用在句型: “Its +adj +that 从句”中. 6) 用作形式宾语, 用来代替动词不定式. make /think /feel/find + it + adj (名词)+ to do sth .二.物主代词.第一人称第二人称第三人称单数复数单数复数单数复数形容词性myouryouryourits/his/hertheir名词性mineoursyoursyoursits/his/herstheirs1. 形容词性的物主代词作定语放在名词前，不能单独使用。2. 名词性的物主代词，后面不能加名词。名词性的物主代词常与of 连用。 Our classroom is as big as _(they) . This is a friend of _(my).注: 1)名词性的物主代词相当于形容词性的物主代词加一个名词.（名词性的物主代词=形容词性的物主代词+ 名词） 2)形容词性的物主代词与own 连用时,后面可跟名词也可不跟名词. My own house = a house of my own 三.反身代词单数复数第一人称myself ourselves第二人称yourselfyourselves第三人称himself/herself/itselfthemselves记忆小窍门:反身代词有规律,第三人称宾格加self.其余都要物主加self,复数ves来把f替.反身代词的常用搭配: enjoy oneself hurt oneself teach oneself = learnby oneslf all by oneself help oneself to look after oneself leave sb by oneself lose oneself in say to oneself for oneself dress oneself improve oneself see oneself in the mirror四.指示代词 1.近指: this these 远指: that those 2.用法: 1)that those 常用来代替前面出现的人或物,以避免重复. That代替可数名词的单数或不可数名词. Those 代替复数名词. The weather in Guangdong is hotter than _ in Qinghai . The books in that shop are cheaper than _in this shop. A.this B.that C.one D.those 2)this ,that 可代替句子或句子的一个部分,that代替前面提到的句子而this代替下面提到的句子. He had a bad cold ,that is why he didnt come . 3)在电话用语中,this 代替自己,而that 代替对方. This is Tom speaking . Who is that ?五.不定代词的区别.1.one与it 的区别 One 代替同类事物中的一种. 而it代替上文中出现的某事物. This book is a good one . May I borrow it ?2.some与any 的区别 一般情况下,some用于肯定句,any用于否定,疑问句,条件句中.但在表建议的疑问句中,仍用some 代any. 常用于could / would / May 开头或what about /how about . 的句中。 May I have some water ? He asked me for some paper , but I didnt have any .3.many与much的区别 Many+可数名词的复数 Much+不可数名词 都相当于 a lot of +复数名词/不可数名词 注:a lot of 不能用于否定句中. 否定句中用many /much .4.a few /few /a little /little 的区别表否定(几乎没有)表肯定(有一点/几个)修饰可数名词fewa few修饰不可数名词littlea little The story is easy to read . there are _ new words in it . Hurry up ! There is _ time left .5.each / every 的区别 each 表示两者或两者以上的人或物中的每一个.而every 表示三者或三者以上的人或物中的每一个. There are trees and frowers on _ side of the street . _ student has read a story .注:each 可以与of 连用, each of 作主语时,谓语动词用单数.而every 不能与of 连用.只能放在名词前作定语. Each of us _(study )hard .6.no one 与none 的区别 no one 表示没有人, 不能与of 连用. 而none of +复数名词/ 代词，作主语时，谓语常用单数。. The boys were all tired , but _ of them stopped to have a rest .7.both /neither /either /all / none / any 的区别都都不任何一个两者之间bothneithereither三者或三者以上allnoneanyThere are many trees on _ side of the river . A. both B.any C.either D.all 注: 1). both 的否定词是neither , all的否定词是none.2).both of 作主语时,谓语动词用复数. neither of作主语时, 谓语动词用单数.Neither of the answers _(be) right .Both of my parents _(be) workers. 3).词组 A) both and 连接两个主语时,谓语动词用复数. 同义词组:not only but also 反义词组: neither nor Not only you but also she likes watching TV.= _ you _ she like watching TV .= You like watching TV , _ _ she .B) either or 或者或者 , neithernor 既不也不 连接两个主语时,谓语动词实行就近原则.Neither you nor he _ (be ) right .One of Lily and Lucy is going to the park. = _ Lily _Lucy _ going to the park.C) either 也可用于否定句中的 “也”D) neither 也可表示 “ 也不” 句型: neither sb 某人也不怎么样. If you dont go there , _ _ I . (我也不去)4) how many /how much 的回答:用none回答. Who 的回答:用no one 回答. What 的回答:用nothing 回答. How many students are there in the classroom ? _. Who can answer the question ? _. A. None B.No one C.Nothing 8.other /the other /others /the others 的区别(空)后面没有名词(空)后面有名词有数量限制(特指)the othersthe other没有数量限制(泛指)othersother 注: 1) one the other 表示两者之间的一个另一个 2) some others 表示一些 一些3) another 表示三者以上的不确定数目中的另一个. 只能修饰可数名词的单数.但 another +数字+ 复数名词= 数字+ more +复数名词 表示 “ 另外几个” Would you like _ apple ? I have two brothers , one is a teacher , _ is a worker . Some are cleaning the classroom , _ are sweeping the window . There are 20 teachers in our school . Eight of them are men teachers ,and _ are women teachers everyone 每个，人人，大家不与of 连用every one每个人、物可与of 连用9.Every one of us has seen the film . Everyone should do their best .10.复合不定代词.someany noeverythingsomethinganythingnothingeverythingonesomeoneanyoneno oneeveryonebodysomebodyanybodynobodyeverybody 注: 1.复合不定代词作主语时, 谓语动词用单数. 2.形容词修饰不定代词时, 形容词放在不定代词之后.3.动词不定式修饰不定代词时, 动词不定式放在不定代词之后.4.复合不定代词用于反义疑问句中, 1)指人的不定代词, 其反义疑问句中的主语用he 或they . 2)指物的不定代词, 其反义疑问句中的主语用 it .5.any ,anything ,anyone, anyboby 也可用于肯定句中,表示 “任何/任何物/任何人”Everything _(begin ) to grow in spring , _ _ ?Is there _(一些有趣的事)in todays newpaper ?I want something _ (eat ).中考专题四：数词基数词: 表示人或事物数量多少的词.序数词: 表示人或事物的顺序的词.一. 基数词.1.基数词的读法. 1)1-12 : one two three four five six seven eight nine ten eleven twelve 2)13-19: 词尾加-teen :thirteen fourteen fifteen sixteen seventeen eighteen nineteen 3)20,30,40,50,60,70,80,90 : 逢十词尾加-ty :twenty thirty forty fifty sixty seventy eighty ninety 4)21-99: 在十位与个位之间加连字符构成. 21- twenty-one 99-ninety-nine 5)101-999 :先说几百, 再加and ,再加末尾两位数或个位数. 101-one hundred and one 238-two hundred and thirty-eight 6)1000以上的数:先将数字从右往左数,每三位数用一个逗号隔开, 从右往左第一个逗号表示 “千”读thousand 第二个逗号表示 “百万”读million 第三个逗号表示 “十亿”读billion 18,657,421-eighteen million ,six hundred and fifty-seven thousand ,four hundred and twenty-one.二. 序数词基数词变序数词 口诀: 基变序,有规律,词尾要加th .一二三,特殊记,词尾分别tdd(first second third ) 八去t ,九去e,ve要用f替.ty变作tie,再加th莫忘记. 若遇几十几,只变个位就可以.三. 数词的应用.1.表编号. 结构:名词(首字母要大写) + 基数词 = the +序数词 +名词 Lesson One = the first lesson 注：有些编号，一般仅用第一种表达法。 Room 101 101号房间2.序数词前一般加定冠词the 但序数词前与不定冠词a /an 连用时,表示 “又一,再一” Youve done it three times .Why not try _fourth time ? A.a B.an C.the D./3.数词前加every ,表示每/每隔 . every ten days =every ninth day 每十天(每隔九天) 注:every +基数词 +复数名词 = every + (序数词-1) +单数名词4.基数词的复数形式表示年代和年龄 1)表示年代: in the + 年份的复数 在几世纪几十年代.在十九世纪七十年代. _. 2)表年龄: in ones + 整十的复数 表示在某人几十岁时在他四十岁时: _.5.hundred / thousand /million /billion 1).若hundred / thousand /million /billion 前有基数词时,其后不加s,也不加of .若没有时 ,既加s 也要带of .Every year _ visitors come to China .There are two _ students in our school . A.thousand B.thousands C.thousands of D.thousand of 2).若其前有a few 、many、several 修饰时，通常用复数，后接of. 3).若名词前有the修饰时，用单数，后接of Two _the students in our school are from the countryside . A.hundred B. hundred of C.hundreds of D.hundreds 6.几个半的表达法: 基数词 + and + a half +名词复数 = 基数词 +名词(单数/复数) +and +a half two and a half hours = two hours and a half 7.时刻表达法: 1)整点: 基数词 + oclock 2)几点几分: A).直接读法: 先读小时 ,后读分钟 3:25 - three twenty-five B).间接读法: a)30分钟. 分钟+ past + 小时 3：25 -twenty-five past three b)30分钟. ( 60-分钟 )+ to + (小时数+1) 3:55 - five to four c) 30 分钟 = half 15分钟=a quarter 45分钟= three quarters 3:30 -half past three 3:15-a quarter past three 3:45 -a quarter to four 8.日期表达法: 结构: 1).月 日,年 (日用序数词,年用基数词) 注:年份的读法: 先读前两位数,再读后两位数. 读日时要加the.1900-nineteen hundred 1807-eight and seven (eight o seven)2008-two thousand eight 2007年3月21日.- March the twenty-first ,two thousand and seven. 2).日 月 年 (the +序数词+of +月, 年)2007年3月21日-the twenty-first of March ,two thousand and seven.9.分数词的表达法: 1).结构: a).分子用基数词,分母用序数词. b).当分子大于1时,分母加复数. 3/4- three fourths (three-fourths) 2).注意:a).分数词的几种特殊形式. 1/3one third = a third 1/4one fourth = a quarter 1/2one second = a half 3/4three fourths = three quarters b).分数词作主语时, 谓语动词根据分数词后面的名词来确定. Two fifths of the milk _(be ) drunk by Tom . One third of the students _(be )girls .中考专题五：介词一介词at/ in /on .1.表示时间：1).表示某一具体时间点，某一时刻/ 年龄 at six oclock at noon at that time at the moment at the age of at night 2)in表示时间段,一天的三个时间段以及月份,年,季节,世纪,人生的某个时期(某人几十岁时) in the morning/afternoon /evening in spring /in 2007/in March in the twenty-first century in his fifties3)on表示星期几/某一具体的日子/具体某天的上午/下午/晚上,表示一天中的三个时间段名词前有修饰语或后有修饰语时.On Monday on New Years Day on Sunday morning on a rainy night on the evening of April 1st ,20072表地点:1)at 一般指较小的地点或较具体的位置 at the station at the cinema 2)in 表示在较大的地点或一个有限空间里. in China in the classroom 3)on 指在某物体的表面上. on the desk注意: 写街道时,若有门牌号用at ,否则用on / in 都可. He lives at 270 DongChangan Street.二.介词in /on / to 表方位:1.in表示A地在B地范围之内.(包含关系) Tanwan is _ the southeast of China .2.on表示A,B地接壤.(外切关系) Hubei is _ the north of Hunan .3.to表示A,B两地有一定的间距.(外离关系) Japan is _ the east of China .三. between / among 在之间1.between :指两者之间. 在.之间.2.among :用于三者或三者以上人或物之间. 在之中. You sit _ him and me . The song is popular _ the students.四.after / in 在之后1. after 1)after + 时间段. 表示以过去某一时刻为起点的一段时间之后, 用于过去时.2)after 作介词. after doing sth 2.in +一段时间. 表示说话时或以现在为起点的将来一段时间之后.用于将来时. He came back _ two days . He will go home_finishing his homework . He will come back _ two days .五.with / in / by 表示 “用”1.with 表示 “用” 一般指有形的工具 / 手段 / 人体器官. He cut the apple into halves _ a knife . 注: with 表伴随, “带有,含有” He came in _ a big smile on his face .2.in表示用某种语言,方式,途径. 或书写/绘画所用的材料. 也可表交通方式.Can you say it _English ?He wrote a letter _ blue ink .3.by表示乘坐交通工具, 表示方式,方法I study for a test _ working with a group .He makes a living _ selling newspapers .注意: 同义词组1).by phone = on the phone 2).by car = in a car 3).in pen = with a pen = with pens 六.across / through / over / by 经过1.across 指横穿,穿过. 表示动作从某一物体表面上经过.2.through 指穿过,透过,表示从某一物体空间内通过.3.over 表示从某人或某物的上空经过或越过,不与表面接触.4.by 表示从某人/某物的旁边经过. Can you swim _ the river ? the elephant is so big that it cant go _ the gate . I dont think anyone can jump _ the fence. I walked _ the bank of China yesterday .七.in front of / in the front of 1.in the front of 表示在.内部的前面2.in front of 表示在外面的前面 There is a desk in _ front of our classroom . There is a big tree in _ front of our classroom.八其它介词的用法：1.at的其它用法.1).表示 “从事或正在做某事”,其后加的名词往往不加冠词. She is at work now = She is working now .2)at表示 “价格或速度” The train ran at 120 kilometres an hour .2.in的其它用法:1)in表示 “在方面” 词组:do well in = be good at be weak in 2)in 表示 “穿着”后接表颜色的词或衣服. 词组: be in +衣服 = be wearing +衣服3)in作副词, “在家” = at home 3.like 的用法:1).像/和一样. 常与系动词连用. 词组: look like sound like 2).与what 连用, “是什么样子, 怎样”. What is he like ? He is kind .4.off的用法:1).从下来, 脱离某物体. 词组: fall off 2). “休假”通常放在时间名词之后. 词组: have +时间+ off He hasnt had a night off for two hours .5.except / besides 1).except 除了.之外, 都. . 不包括在范围之内. 注: nothing but 除了之外,什么也没有.2).besdies除了之外,还有 . 包括在范围之内. We all went swimming _ Lucy . There is _ a letter in the box . We study Japanese and French_ English .6.with / without 1).with具有,含有 -反义词: without 没有词组: with the help of = with ones help =because of = thanks to without ones help 2).without 的用法: A).without + sb./ sth. 没有某人或某物 B).without + doing sth . He left here without_(say ) “Goodbye”to usC). without sth 常与if 引导的否定的条件句. If there is no water , we cant live .= We cant live _ _ .7.on the tree /in the tree on the tree 表示 “树上本身长的东西” 在树上. 而in the tree 表示 “外界的物体进入树中” 人或物在树上. There are some apples _ the tree . There is a boy _ the tree.8.since / for 注: since / for 用于现在完成时.1).since : a).since +时间点 b). 现在完成时+ since +一般过去时 c).since +一段时间+ ago.2)for: for +一段时间= since +一段时间+ ago9.be made +介词的区别: be made of 由制成 (看得见原材料) be made from由制成 (看不见原材料)be made in +地点 由哪儿生产 be made by sb. 由某人制造10.表示 “数量的介词”about , round around over 1). about , round around表示 “大约” 2).over 表示 “超过”= more than.11.inside / outside Inside 在里面 -反义词:outside在.外面12.in the wall /on the wall in the wall 表示“门窗在墙上” on the wall 表示“某东西张贴或挂在墙上”九.不用介词的情况:1).当时间状为: tonight, today, yesterday, tomorrow 等时,不用介词. What are you going to do tonight ?2).含有this, that, these, those, last, next, every, each等时间状语. He went to Wuhan last week .3).以all 开头的时间状语前面不用介词. He has worked all day .4).以some ,any, one 等构成的时间状语前不用介词. He met a bad man one cold morning .= He met a bad man on a cold morning .中考考点六：连词一并列连词和连词短语 并列连词用来连接平行的词、词组或从句。常见的连词有and ,but ,or ,so ,bothand , eitheror ,neithernor , not only but also 等。1. and 1).and 表示 “和、且”在肯定句中连接并列的成分。 He is laughing and talking . 2).祈使句+ and , “and” 表示“那么”之意。= If Study hard , and you will succeed .= _ _ study hard , you will succeed . 3).adj / adv + and + adj /adv 表示“渐渐”。 He makes mistakes again and again .2.but 表示转折关系的连词，意为“但是” He is poor ,but honest .3.or 1).or 有 “或”的意思，表示一种选择 Would you like tea or water ? 2). “祈使句,or ” or 表示否则。= If not , . . Study hard , or you will fail. = _ you _study hard , you will fail . 3).or 用在否定句中表示并列关系。 He cant read or write .4.both 1).both “两者都”, 后面的名词、动词都用复数。 Both the answers are right . 2).both of . Both of us are students . 3).both and Both you and she are right .5.either/ either or 1).either “两者当中任何一个”,后有of 时接名词的复数形式，无of时接单数名词，动词用单数形式。You may wear either of the hats. 2).either or “不是就是,或者 或者.”动词与临近的主语保持一致。即 “就近原则”.Either you or he has to go = Either he or you have to go .6.neither /neither nor 1).neither “两者当中都不”,后有of 时接名词的复数形式，无of时接单数名词，动词用单数形式。 Neither of the answers _(be) right . 2).neither .nor “既不.也不”动词与临近的主语保持一致。即 “就近原则”. Neither you nor I am right .= Neither I nor you are right .二从属连词从属连词是引导从句的连词。