高中英语语法系统讲解之三介词和连词

高中英语语法系统讲解之三

介词和连词

介词

一. 介词的语法作用

用来表明名词、代词与句中其他词的关系的词叫介词。介词是虚词，不能重读，不能单独作句子成分，需要和它后面的词共同充当句子成分。介词及其宾语在句中作定语、状语、表语及宾语补足语等成分。如The key to the door is missing.(定语) Marx stayed in Belgium for some time and then went to France.(状语) Japan is to the east of China.(表语)

Make yourself at home.(宾语补足语)

二. 介词的分类

1. 根据介词的构成形式可将介词分为以下几类：

简单介词：at, by, for, in, on, from, during, past等

复合代词：out of, onto, into, insede, without等

短语介词：because of, instead of, in front of, by the end of等

双重介词：from behind, from around, till after等

动词的-ing形式介词：including, considering, regarding, concerning等

2. 根据介词的意义可将介词为以下几类：

○1表示方位和空间关系的介词：at, round, in, over, below, in front of, outside, among, away from, around, on, under, above, behind, inside, near to, off, beyond, past, across, over, up, opposite

○2表示时间的介词：at, in, around, between, since, during, till, after, on, about, round, for, until, by, before, from …to …

○3表示工具、手段、方式等的介词：like, in, with, by

○4表示其他含义的介词：without, besides, with, except, instead of

三. 常用介词的用法

1. 表示时间的介词

○1at, in, on和by

A. at的用法：

a.时间的一点、时刻等，如at 12:00, at noon, at night, at midnight, at dawn, at daybreak

b. 较短暂的一段时间，可指某个节日或被认为是一年中标志大事的日子，如at Christams,

at New Year, at the Spring Festival

B. in的用法：

a. 表示在某个较长的时间内（如世纪、朝代、年代、月及泛指上午、下午和傍晚等），

如in the 1980s, in Qing Dynasty, in October, in the morning

b.表示在一段时间之后，如I’ll be back in an hour.

C. on的用法：

a.用于表示具体的日子或一个特定的时间，如某日、某节日、星期几等。如on October 1st,

on a rainy day, on National Day

b.用于表示特定的上午、下午或晚上。如on the eve of victory (胜利前夕)，on the morning of January 3rd, on

the afternoon of his arrival

c. 准时、按时on time

D. by的用法：

a. 表示“不迟于，在（某时）前”，如He must have arrived there by now.

b. 表示“在……间”“在……时间”，如He worked by day and slept by night.

温馨提示：当时间名词前被this，that，last，next，some，every等词限定时，通常不用任何介词。

○2after与in

二词均可表示在某一段时间后，但该时段的起点不同。

A. in的用法：

in表示以此刻为起点的将来一个时段之后，常与将来时态的谓语动词连用。

如My father will be back from abroad in three days.

B. after的用法：

a.与表示一段时间的词连用，常与过去时态的谓语动词连用，这时相当于“一段时间+ later”如He left home

and went to the front after two days / two days later.

b.与表示时间点的词连用，常与将来时态的谓语动词连用。

如I’ll go and see her after three o’clock.

易错误区：“in the past”意为“在过去”，与过去时态的谓语动词连用。如In the past, no villagers dared do that；“in the past / last + 时间段”意为“在过去的……中/ 内”，表示从现在算起过去的一段时间，包括此时此刻在内，常与现在完成时态连用。如In the past / last few years, great changes have taken place in this village.

○3during, for, from和since

during除具备in表时间段的用法外，还可指在某一活动过程中，如during the night，during the fire，during the meeting。for后接时间段的名词词组，表示行为状态持续了多久，如I have lived in this city for more than 10 years. from接时间点的名词词组，表示行为或状态的起始点，而不涉及其持续时间的长短，如My younger sister began to learn dance from the age of five. since接时间点的名词词组，不仅表示行为或状态的起始点，而且还强调该行为或状态从起始点一直持续到此时此刻，因而与延续性动词的现在完成时连用，如I have been working in this factory since I graduated in 1993.

2. 表示空间和方位的介词

○1above, over, on, below, under, beneath

A. above侧重于相对水平高度，不一定在正上方，其反义词是below。如The sun is above the mountain in the east. The position he pointed to was below the sea level.

B. over侧重于垂直高度，即位于正上方，其反义词是under。如Be careful, there is a heavy box over your head. The little mouse is under the table, so it is not easy to find it.

C. on侧重于与物体表面接触，其反义词是beneath。如There are some stamps on the desk.

○2across, over, through, past

四个词都与表示运动的动词有关。across意为“横穿，穿越”，表示运动发生在物体的表面；over意为“跨过，越过”，表示运动发生在物体的上方；through意为“穿过，通过”，表示运动发生在某物的空间；past意为“从旁边经过”，表示运动发生在某物旁边。

如The Great Wall winds its way from west to east, across deserts, over mountains, through valleys, till at last it reaches the sea.

After the meeting, I went past the past office straight to my home.

○3at, in, on 三者均表示地点，“在……处”

A. at

a.用于指较小的地方，如We’ll meet each other at the park.

b.用于门牌号码前，如My grandparents live at 105 Beijing Road.

B.in 用于指较大的地方，如She lived in Hong Kong for 20 years.

C.on 一般指与面或线接触，如Put the pictures on the wall.

○4near, by, beside, at 四个词都表示“在……附近”，但侧重点不同。

A. near表示相对的“近”，而实际距离可能并不近。

如A new hospital is being built near our school.

B. by和beside都表示“靠近”，但beside比by更具体地表示出“在……旁边”的意思。

如I planted an apple tree by the river. The girl was sitting beside her mother.

C. at表示“在……旁边”之意，但多表示有目的的和所处的位置，而by和beside仅表示位置关系。如We are sitting at the desks listening to our teacher.

○5to, for, toward(s)

用于表示来往行动动词之后，表示行动的方向，多用to，如go，come，walk，run，dash，rush，move，fly，return，lead，take等；用于表示“起程，出发，离开”的动词之后，多用for，如leave，start，set off等；用于表示“朝……方向”时，to和towards是同义词，不表到达，而to不仅表方向，还表到达。

如After the soldiers got well prepared, they set off for the front.

The plane is flying towards the north, but it’s difficult to decide which area it’s flying to.

○6in, on, to在方位名词前的区别，三词都可表示两地之间的位置关系。

in表示在范围之内，如Shandong Province is / lies in the east of China.；to表示在某范围之外的地方，如Japan is / lies to east of China.；on表示“毗邻、接壤”，如Mongolia is / lies on the north of China.。

○7between，among 二词均表示“在……中间，在……之间”。

between表示在二者之间，有时between之后也可能出现三个或三个以上的宾语，但这时所强调的仍然是其中每两者之间的相互关系，如This secret is only between you and me. 而among指在三者或三者以上之间，如We’ll visit a town among the mountains.

○8in，on二词均可表示“在……上”，描写两个物体的接触情况。

in侧重于接触的深度，如We found a square hole in the west wall.

on侧重于表面接触，如There is a map of the world on the wall.

温馨提示：○1英语中若打击某人的脸、眼、嘴、胸、腹等部位时，用in，如They hit the boy in the face and then ran away.

而打击头、额、鼻、耳、颈、肩、腿等部位时，用on，如The teacher patted the boy on the head and comforted him.

○2表示植物本身生长出来的叶、花、果等，用on，如There are lots of apples on the tree.

○3表示植物本身以外的人或动物“在树上”，用in the tree，意指被枝叶遮掩其中。

如Birds often play in the tree.

○9after，behind二词表示“在……之后”。

after多指动作顺序的先后，behind表示静态位置的前后。二者表示位置时常可通用。

如Winter comes after autumn. Behind the hospital stood a school.

Shut the door after / behind you.

3. 表示工具、手段、方式的介词

○1by，in，on三词都表示旅行的方式

A. by

a.不涉及交通工具的名词时用by，名词前不带冠词，如by sea, by water, by land, by rail

b.涉及交通工具的名词时用by，但名词须用单数，其前面不加冠词或任何修饰语，如by bike, by taxi, by

plane, by ship / boat, by train, by spaceship

B. 当旅行方式涉及到确定特指的交通工具时，用on或in，名词前应有冠词、物主代词、指示代词等修饰

语，如travel to New York in this plane; leave on an early train; go to school on my bike

温馨提示：步行、骑马等均可用on，如on foot, on horseback, on a horse, on the camel

○2with，by，in三词均译为“用”，表示行为的工具、手段或方式。

A. with用于有形的工具或身体某些器官等，其后的名词多被冠词、物主代词等修饰。

如They are digging with a pick / spade.

We see with our eyes, hear with our ears, and walk with our legs.

B. by，in，on，over，through等多用于无形的工具或方式手段。

如by hand, in ink, on the telephone, over the radio, through the telescope

温馨提示：○1使用语言、原料、材料时用in表示，如in English / Japanese, in blue ink

○2表达“用……方法/ 式”时，所用介词分别为：in this / that / the same … way;

by this / that … means, by means of …; with this / that … method

4. 表示原因的介词

○1at，for，with三词均可组成介词短语，表示行为或状态的原因、动机或理由。

A. at常与表示感情色彩的动词、形容词或过去分词搭配，后接表示具体事物的名词。如We were excited / happy / fightened at the news. I was angry at her words.

B. for和with后接表示感情的抽象名词，其中with侧重于随着心理变化而发生的感情变化。

如She often hangs down her head for shame. He went red with anger.

○2because of，due to，thanks to三个词组均意为“由于，因为”

A. because of“因为，由于”，通常作状语，位于句首或句尾。

如The sports meet will be put off till next Saturday because of the heavy rain.

B. due to“因为，由于”，通常作表语。如His illness was due to smoking and drinking.

C. thanks to“幸亏，多亏”，既可用于褒义，又可用于贬义，多位于句首。

如Thanks to the Party’s good policy, the famers are now living a happy and rich life.

5. 其他易混介词

○1about，on，of表示“关于”

A. about侧重于与人或事物有关的事迹或情况。

如The Red Army man told us a story about Chairman Mao.

B. on侧重于阐述或论及相对重大或深奥的理论、学术等问题。

如Who made the report on the situation in the Middle East?

C. of在与tell，read，know，think等动词连用时，侧重于粗略涉及，而about涉及的情况则详细得多。如---Do you know about that man over there?---No, I know little of him.

○2in和of表示比较范围，均可引出一个可供比较的范围，适用于形容词和副词的最高级，指三者或三者以上的人或事物的比较。

A. in表示限定在某个范围内的最高级。如Mary sings best in my class.

B. of表示同一类人或事物中的最高级；用于同类两者之间的比较，但比较级前须加定冠词

the。如Of all the boys, Tom runs the fastest.

○3表示“包括、排除”的介词的区别：besides，except，but，other than，except for，except than / when

A.用于否定句时，besides，except与but可相互替换。如No other students passed the difficult maths exam

except / beside / but Lin Tao and Wu Dong.

B.用于肯定句时的用法

a. except意为“除……之外”（不再有），如We all passed the exam except Tom.

b. besides意为“除……之外”（还有……），如We all passed the exam besides Tom.

温馨提示：besides在句中的位置较灵活，可放在句首，亦可放在句中；而except多放在句中。此外，except前几乎总有all，any，every，no及其复合词等；而besides前可用，也可不用，依句意而定。如He answered all the questions except the last one.

I have a few friends besides you.

c. except for意为“除了因为……”，表示除去整体中的一部分，它所叙述的事实或细节部分地修正句子的

主要意思。如The composition is good except for a few spelling mistakes.

C. except和but / other than都可接名词、代词、动名词、动词原形，可以互换；但except后接副词、介

词短语、when从句等时，but / other than不可替换except。

如He has always been in high spirits except recently.

The window is never opened except in summer.

D. but，except后都可接thatong句作宾语，二者可互换。

如I asked nothing from him but / except that he should write to me every other week.

E. 以上比较了except，besides，but作介词的区别，另外，besides还可用作副词，意为“而且，还有”。

如I don’t want to go; besides, I am too tired.

This is my best suit; I have two other besides.

6. 介词与某些词类的搭配

○1名词与介词的固定搭配

A. 要求to的名词：key，answer，visit，apology，introduction

B. 要求in的名词：interest，satisfaction，expert

C. 要求on的名词：mercy，congratulation

D. 要求其他介词的名词：prize for，respect for，victory over，struggle with

○2形容词与介词的固定搭配

A. 要求at的形容词：afraid，angry，good，bad，clever，surprised，excited，puzzled，frightened

B. 要求of的形容词：afraid，sure，certain，full，tired，fond，proud，worthy

C. 要求with的形容词：angry，strict，careful，busy，popular

D. 要求in的形容词：weak，strict，rich，interested，successful

E. 要求to的形容词：next，good，polite，kind，cruel，rude，known，married，close，similar，due

F. 要求for的形容词：sorry，famous，fit，unfit，eager，anxious，hungry

G. 要求from的形容词：far，different，free，safe，absent，tired

H. 要求about的形容词：sorry，worried，anxious，careful，sure，certain

温馨提示：同一形容词与不同的介词搭配其含义不同。如

He is good to her. He was tired of the work.

He was tired from the work.

7. 关于介词的省略

○1在某些名词词组前，可以省略。如(in) that day, (on) Mondays, (in) the year before last

○2在of + 形状、大小、年龄、面积、材料结构中，of常省略。

如When I was (of) your age, I knew much less than you.

The desks in our class are (of) the same color, material, shape, height and length.

○3在肯定句中表一段时间的介词for常省略。

如He has been waiting for you (for) a whole afternoon.

○4在句子中，如并列的介词相同，可省略后面的介词。

如You can wear that outfit in summer and (in) winter.

温馨提示：如并列的介词不相同，相关的介词必须列出：

○1The children were interested in and disgusted by the movie.

○2It was clear that this player could both contribute to and learn from every game he played.

○3He was fascinated by and enamored of this beguiling woman.

○5在某些习语中的省略。如be busy (in) doing sth, (in) … way …, next (to) , have difficult / trouble (in) doing sth, stop … (from) doing sth, spend … (in) doing sth opposite (to),

have a good time (in) doing sth, waste …(in) doing sth, pass time (in) doing sth

kill time (in) doing sth, (in) this / that way, (at) any time, near / nearer / nearest (to)

prevent / stop …(from) doing sth, It’s (of) no use (in) doing sth

附：常见介词to，at，on，in，from和for的常见搭配

1. to的常见搭配

○1动词+ … + to …

A.动词+ to：adjust to“适应”，attend to“处理；照料”，agree to，amount to“加起来达……”，belong

to，come to“达到”，drink to“为……干杯”，get to，happen to，hold to“紧握”，lend to，listen to，occur to“想起”，object to，point to，see to，respond to“参与；涉及”，refer to，reply to“回答”，stick to“坚持”，turn to“求助”，write to

B. 动词（+sth）+ to + sb：announce to“通知某人”，describe to“向某人描述”，explain to，express to，

mention to，nod to，report to，say to，shout to，suggest to，speak to，talk to，whisper to“和某人低声耳语”

C. 动词+ sth / sb + to + sth / sb：add to，compare to“比作”，carry to，devote to“致力于”，introduce

to“介绍给”，invite to“邀请参加”，join to“连接到”，leave to“委托给”，reduce to“下降至”，sentence to“判处”，take to

○2be + 形容词/ 过去分词+ to：be alive to“觉察；晓得”，be attentive to，be awake to“知晓”，be blind to“缺乏眼光”，be close to“紧挨着”，be common to“对某人来说很普通”，be contrary to “违反；反对”，be devoted to“致力于”，be deaf to“不愿意听”，be exposed to“暴露；遭受”，be fair to“对……公平”，be familiar to“为……所熟悉”，

be grateful to“对某人心存感激”，be good to“对……有好处”，be harmful to“对……有危害”，be important to，be kind to，be known to，be married to，be moved to，be near to，be necessary to，be opposite to“在对面”，be opposed to，be pleasant to“合某人之意”，be proper to“专属”，be polite to“礼貌待人”，be rude to“粗暴对待”，be relative to“与……有关”，be strange to“不习惯”，be similar to“类似”，be suitable to“适合”，be true to，be thankful to，be useful to，be used to ○3to + 名词：to a degree“在某种程度上”，to date“到现在为止”，to one’s feet“跳起来”，to one’s mind“照……看来”，to one’s surprise，to one’s taste“符合胃口”，to oneself“独自享用”，to order “订做”，to the letter“不折不扣地”，to the point“中肯地”

2. at的常见搭配

○1动词+ at：arrive at, call at“访问某地”，catch at (it)“当场抓住”，fire at, glance at, glare at, grieve at“忧伤”，knock at, laugh at, look at, pull at“拉扯”，rejoice at“因……高兴”，smile at, shoot at, stare at, thrust at“刺向”，tear at“撕”，tremble at“颤抖”，wonder at“对……感到吃惊”，work at

○2be + 形容词/ 过去分词+ at：be angry at, be alarmed at“对……保持警觉”，be astonished at, be bad at, be clever at“对某事很灵巧”，be delighted at“高兴”，be disgusted at“厌恶”，be disappointed at“对……失望”，be good at“擅长”，be impatient at“对……不够耐心”，be mad at“狂热于”，be pleased at“对……感到高兴”，be present at“出席”，be satisfied at“满意”，be surprised at, be shocked at, be terrified at, be quick at

○3at + 名词：at a distance, at a loss, at a time, at all, at any cost, at best“最多，充其量”，at first, at hand“手头”，at heart“在内心里”，at home, at last, at least, at most“最多”，at once, at present

3. on的常见搭配

○1动词+ … on …

A.动词+ on：act on“对……有作用”，bring on“促使；导致”，call on, count on, carry on, depend

on, feed on, figure on“料想；推断”，go on, have on, insist on, keep on, lean on“依赖”，live on“以……为生”，pull on“迅速穿上”，put on, switch on“接通（电源）”，take to, turn on “接通（电源）”，work on, wait on“侍侯”

B. 动词+ sb（sth）+ on + sb（sth）：base on, congratulate on, fix on“固定”，have mercy on, have

pity on, keep watch on, spend on

○2be + 形容词+ on：be dependent on“依赖”，be hard on, be impressed on“对……印象深刻”，be keen on“渴望”，be strict on“对……严格”

○3on + 名词：on board“乘（车、飞机）”，on call“听候召唤”，on duty, on earth, on fire“着火”，on foot, on guard, on hire“受雇”，on holiday

4. in的常见搭配

○1动词+ … + in …

A. 动词+ in：believe in, break in“闯入，打断”，bring in“引起；产生；带来”，call in“下令收回”，

fill in, get in“收获”，hand in, involve in“涉及”，lie in, result in, share in“共享”，succeed in, take in, turn in

B. 动词+ sb / time / money + in：help sb in, spare time / money in, spend time / money in,

waste time / money in

○2be + 形容词+ in：be active in, be absorbed in, be busy in, be born in, be concerned in, be clothed in“穿着”，be disappointed in, be diligent in“勤于”，be experienced in, be employed in“任职于”，be engaged in“忙碌”，be expert in, be excellent in, be interested in, be lacking in, be rich in, be slow in, be successful in, be skilled in, be strict in, be weak in

○3in + 名词：in advance, in all, in bed, in body“亲自”，in brief“简明扼要”，in case“万一”，in charge“主管”，in danger, in debt, in despair, in force“大量地；有效”，in full“全部地”，in flower“开花”，in general, in itself, in love, in order, in person, in public, in progress“有进展”，in practice“在实践上”，in rags, in research, in return, in ruins“一片废墟”，in short“总之”，in theory“理论上”，in trouble, in tears, in time, in turn, in vain, in view“看得见”

5. from的常见搭配

○1动词+ … from …

A.动词+ from：come from, date from, depart from“违背”，die from, escape from, fall from, hang

from, hear from, learn from, return from, rise from, result from, suffer from

B. 动词+ sth / sb + from + sth / sb / a place：borrow from, choose from, keep from, prevent from,

protect from, receive from, remove from, save from, separate from, stop from

○2be + 形容词+ from：be absent from, be different from, be far from, be hidden from, be made from, be tired from“因……而疲倦”

○3from … to …：from bad to worse, from beginning to end, from cover to cover“从头到尾”，from China to Peru“到处”，from day to day, from first to last, from hand to mouth, from head to foot, from mouth to mouth, from start to finish“从头到尾”，from top to toe“从头到脚”，from time to time“不时地”，from top to bottom“彻底地”

6. for的常见搭配

○1动词+ … + for …

A. 动词+ for：account for, answer for, apply for, apologize for, beg for, call for“要求”，care for,

enter for“报名参加”，fight for, hope for, inquire for“查询；求见”，leave for, look for, long for, mistake for, plan for, prepare for, provide for“为……提供”，reach for, run for“竞选”，stand for, search for, send for, speak for“陈述意见、愿望”，take for“当作”，wish for, wait for

B.动词+ sb + for + sth：ask for, blame for, excuse for, forgive for, pardon for, pay for, praise for,

punish for, push for“催逼”，reward for, thank for

○2be + 形容词+ for：be anxious for, be eager for, be bad for, be convenient for, be good for, be famous for, be fit for“适合于”，be grateful for“对……心存感激”，be impatient for, be late for, be necessary for, be ready for, be sorry for, be responsible for, be suitable for, be unfit for, be useful for

○3for + 名词：for all, for a song“非常便宜地”，for certain“确切地”，for company“陪着”，for ever, for example, for fear“以免”，for fair“肯定地”，for free“免费”，for fun, for instance, for luck“祝福”，for life“终身”，for long, for nothing, for once“有生第一次”，for oneself “替自己”，for pleasure“为了消遣”，for sale“供出售”，for shame“真丢脸”，for short“简称”，for sport“好玩”，for sure“确切地”

○4动词+ 副词/ 名词+ for：be in for“将遇到”，make up for, go in for, look out for, take sth for granted, have an ear for“对……听觉灵敏”，have a gift for

连词：是连接单词、短语或句子的一种虚词，在句中不单独作任何成份，一般不重读。

一. 连词的分类

1. 按连词的构成可将其分为以下几类：

○1简单连词，如and, if, or, because, but, so

○2关联连词，如both … and …, not … but …, not only … but also …

○3分词连词，如supposing, providing, provided, given

○4短语连词，如as if / through, even if / through, as / so long as

2. 按连词的性质可将其分为以下几类：

○1并列连词，如and, but, or, nor, so, for, as well as, while, when, not only … but also …, both … and …, either … or …, neither … nor, therefore, yet, nevertheless, however等。它们用来连接平行的词、词组或分句。

○2从属连词，如after, when, before, as, while, since, until, till, although, though, if, even if, unless, lest, because, than, that, whether, so that, as soon as, as long as, in order that, as though, suppose (that), provided (that), in case (that), now (that), on condition (that), seeing that, so … that, such … that, as … as, so …as等。它们用来引导从句。

温馨提示：除连词外，连接代词、连接副词、关系代词、关系副词也可以来引导一个从句。

二. 并列连词

1. 表示并列关系的连词：主要表示“和，补充，增加”之意，包括等。如and, both … and, neither … nor,

not only … but (also), as well as等。

如Neither Mary nor Tom came to our party yesterday.

She plays both the piano and the guitar.

He has been to all the countries in the Middle East as well as Europe.

He is not only our teacher but also our friend.

温馨提示：在连接三个或三个以上的名词或相当于名词的短语时，一般应在最后两者之间加and。如He got up,washed his face, had breakfast and rushed to school.

2. 表示转折关系的连词：主要有but, only, while, when, whereas等。

如A great deal has been accomplished, but more remains to be done.

He is riding, while his father is walking in the dust.

Why did you borrow the book when you had one?

He is ill, whereas I am only a little tired.

only表示意义转折，只见于非正式文体。如You may go, only come back early.(only = but)

温馨提示：○1有些词或短语在句中也表示转折意义，如still, yet, however, all the same, after all 等。通常作连接性状语。

如The problem was a little hard, yet I was able to work it out

I explained twice, still he couldn’t understand.

○2while在表示转折关系时，往往连接内容和结构对称的句子。

如I love strong tea while my father loves coffee.

○3both … and … not结构和neither … nor …的区别在于前者表示部分否定，而后者表示全部否定。如Both you and I are not correct. Neither you nor I am right.

3. 表示选择关系的连词：主要有or, either … or, or else, whether … or, otherwise等。如Which do you

like better, tea or coffee?

Either you leave this house or I’ll call the police.

Do it at once, or else! = Do it at once, otherwise you will suffer in some way.

Take a taxi, otherwise you won’t get there in time.

4. 表示因果推理关系的连词：主要有so, for, then, therefore等。

如The air here is polluted, so the crops are dying.

It must be late, for I have been here a long time.

温馨提示：for，because，as，since在用法和意义上的区别：

○1for引导的句子是并列分句，只能后置，并用逗号与前面的句子隔开。主要用来表示推测性原因，或附带解释、说明前一分句的情况。

如The electric current must have been turned off, for the light went out.

○2because用来引导表示直接原因的从句，语气很强，明确地说明因果关系。其引导的从句可置于句首、句末或句中。如He is absent today because he is ill.

for引导分句表示因果关系时，它可以和because互换使用。

如上句也可以说成：He is absent today, for he is ill.

但表示推测性原因，就不能互换使用。如He must be ill, for he is absent today.

○3since，as都是不讲自明的原因，是已知的原因，as的语气比since要弱。

如Since (As) you don’t feel well, you had better stay at home.

三. 从属连词：用来连接分句，表示各分句之间的关系。其可分为引导名词性从句、状语从句的连词和引

导副词性从句的连词。用法详见“主从复合句部分”。