状语从句（一）

　　在复合句中修饰主句或主句中的某一成分的从句叫状语从句。状语从句通常由从属连词或起连词作用的词组引导，有时甚至不需要连词直接和主句连接起来。状语从句根据它表达的意思不同，可分为时间、地点、原因、目的、结果、条件、方式、比较、让步等九类。
　　一、时间状语从句
　　时间状语从句是表示时间关系的从句。可以引导时间状语从句的连词很多，根据意义和主从句之间的时间关系，通常可分为以下几种情况：
　　a．when, while, as, whenever
　　when, while, as表示主句谓语作和从句的谓语动作同时发生或几乎同时发生。
　　1．when
　　①when表示点时间时，从句中用短暂性动词；表示段时间时，用持续性动词。
　　when i got home, my family were already having dinner.
　　我到家的时候，全家已在吃晚饭。
　　（when表示点时间）
　　when they were still talking and laughing, the teacher came in.
　　当他们还在说笑的时候，老师进来了。（when表示段时间）
　　he waved ahello when he saw her.
　　当他看见她的时候，就挥手打了个招呼。（when表示点时间）
　　when you think you know nothing, you begin to know something.
　　当你认为自己一无所知的时候，就开始知道一些事情了。（when表示段时间）
　　注意：
　　当when意思是正当……时候（and at that moment）时，when只能跟在前一分句之后。
　　he was about to go to bed when the doorbel rang.
　　他正要上床，忽然门铃响了。
　　they were watching the world cup when suddenly the lights went out.
　　他们正看着世界杯比赛，突然灯灭了。
　　they had just arrived home when it began to rain.
　　他们刚到家，天就开始下雨了。
　　②有时when表示虽然，尽管的含义，相当于although或since。
　　he walks when he might take a taxi.
　　尽管可以打的，但他还是步行。
　　how can you hope for mercy yourself when you show none
　　既然你不宽恕别人，你自己又怎能希望得到别人的宽恕呢？
　　2．while
　　①while通常表示一段时间，从句中宜用持续性动词作谓语。
　　strike while the iron is hot.
　　趁热打铁。
　　she fell asleep while she was reading the newspaper.
　　她在看报的时候睡着了。
　　②while有时可以作并列连词，表示对比，可译成……而……。
　　i am fond of english while he likes maths.
　　我喜欢英语而他却喜欢数学。
　　we slept while the captain kept watch.
　　我们睡觉而上尉担任警戒。
　　③while有时可引导让步状语从句，意思是虽然。
　　while they love te children, they are strict with them.
　　虽然他们都爱他们的孩子，但却对他们要求严格。
　　提示：
　　虽然during 与 while 意思很相近，但是during是介词，不能引导从句。
　　3．as
　　①as表示点时间时，从句中用短暂性动词；表示段时间时，用持续性动词。as和when两者经常可以通用。
　　the thief was caught as when he was stealing in the supermarket.
　　小偷在超市行窃时被逮住了。
　　i saw jim as when he left the meeting room.
　　吉姆离开会议室时候我看到了他。
　　②as表示 一边……一边……，强调从句和主句中两个动作交替进行或同步进行。
　　they talked as they walked.
　　他们边走边聊。
　　he looked behind from time to time as he went.
　　他一边走，一边不时地往后看。
　　③as表示随着
　　as time goes on, it＂s getting warmer and warmer.
　　随着时间的推移，天气变得越来越暖了。
　　as spring warms the earth, al flowers begin to bloom.
　　随着春回大地，百花开始绽放。
　　4．when, while, as的用法区别
　　①只有当从句表示的是段时间，即其谓语动词有持续性特征时，这三者可以通用互换。
　　i got the news on the radio when while as i was having breakfast.
　　我在吃早饭的时候从收音机里获悉这一消息。
　　②在下列情况下，三者彼此之间不能替换使用：
　　a．as更强调同一时间或紧接的一前一后或伴随着的变化。
　　we listened to the singer sing as he played the guitar.
　　我们听着歌星边弹吉它边演唱。
　　i thought of it just as you opened your mouth.
　　你一张嘴我就知道你要说什幺
　　as he grew older, he became less and less active.
　　随着他年龄的增长，他变得越来越不活泼了。
　　提示：
　　状语从句可放在主句之前或之后，放在主句之前时一般用逗号与主句分开。有时可置于主句中间，前后用逗号。
　　b．when更强调特定时间，还可表示从句中的动作先于或后于主句的动作。
　　when i had given mary the spare ticket, i found my own already gone.
　　当我把多余的票给了玛丽时，我才发现我自己的票已不知去向。（从句动作发生在主句之前，注意主从句的时态）
　　when i finally got there, he meeting had been on for ten minutes.
　　当我最终赶到那里时，会议已开始十分钟了。（从句动作发生在主句之后，注意时态）
　　c．while从句只能表示延续的动作或状态或主从句中动作的对比。
　　she thought i was talking about her daughter, while in fact, i was talking
　　about my daughter.
　　她以为我在谈论她女儿，而事实上，我在谈论我的女儿。
　　d．若表示两个短促动作几乎同时发生时，用as场合多于when。
　　as he finished his speech, the audience burst into applause.
　　他结束讲话时，观众爆发出雷鸣般的掌声。
　　5．whenever
　　whenever是when的强势语，它描述的不是一次性动作，而是经常发生的习惯性动作。
　　you are always welcome whenever you come.
　　无论你何时来都欢迎。
　　whenever we met with diffiulties, they came to help us.
　　每当我们遇上困难的时候，他们就来帮我们。
　　b．before, after
　　1．before
　　before表示在一段时间之前。
　　i must finish all the work before go home.
　　回家之前我必须干完所有的活。
　　you must first learn to walk before you try to run.
　　在想要跑以前，你得先学会走。
　　he had learned english for three years before he went to london.
　　他去伦敦之前已学了三年英语。
　　提示：
　　before 从句往往带有否定的含义。
　　he ran off before i could stop him.
　　我还没来得及阻止他，他就跑掉了。
　　thke it down berore you forget it.
　　趁着还没忘记的时候就记录下来。
　　必背：
　　before 常用句型 it is was will be  before
　　it wil be five years before we meet again.
　　五年以后我们才能再见。
　　it will be not long before you regret what you have done.
　　不用过多久你就会对你所作所为感到后悔的。
　　it was not long before i realized i was wrong.
　　不久我就意识到我错了。
　　it was minutes before the police arrived.
　　过了几分钟警察才到。
　　2．after
　　after表在一段时间之后。
　　let＂s play football after school is over.
　　放学后我们踢足球吧。
　　the sun came out soon after the storm stopped.
　　暴风雨过后不久，太阳出来了。
　　c．till, until
　　1．untiltill用于肯定句时，表示直到 为止，主句必须为持续性动词。
　　we shall wait until till he comes back.
　　我们将一直等到他回来。 (注意它们的拼写)
　　everthing went well untiltill that accident happened.
　　直到发生那意外之前，一切都正常。
　　2． not untiltill表示直到 才 ，主句通常要用短暂动词，这时until和till可用before代替。
　　i didn＂t leave until till before she came back.
　　直到她回来，我才离开的。
　　bells don＂t ring till until you strike them.
　　铃不打不响。
　　peopl do not know the value of their health till until before they lose it.
　　人们直至失去了健康才知其可贵。
　　3．当not until位于句首时，主句中的主语、谓语要使用倒装语序。
　　not until she stopped crying did i leave.
　　直到她不哭了，我才离开的。
　　注意：
　　until引导的从句可以放在主句之前或主句之后，但till从句一般不放在句首。
　　4．在强调句型中一般只能用until，不用till。
　　it was not until she took off her drk glasses that i recognized her.
　　直到她摘下墨镜，我才认出她。
　　d．since, ever since
　　1．since自……以来。表示动作从过去某一点时间一直延续到说话时间为止。主句中通常为延续性动词的现在完成时，since从句中一般用短暂性动词的一般过去时。
　　it has been just a week since we arrived here.
　　我们到这儿刚刚一星期。
　　where haveyou been since i last saw you
　　自上次我见过你之后，你去了哪里？
　　since she was young, she has been collecting stamps.
　　她自年轻时起就一直集邮至今。
　　提示：
　　有时since 从句中也可以用延续性动词，注意它的译法。
　　tom is now working on the farm.it＂s two years since he was a college student.
　　汤姆现在农场上班，他大学毕业已有两年了。
　　2．ever since 从那时起直至现在，此后一直。表示说话者强调主句动作或状态持续时间长，语气比since强。
　　ever since they got married in 1950, they have lived happily.
　　自一xx零年结婚以来，他们一直生得很幸福。
　　3．since还可以用作副词或介词。
　　the big clock was damaged during the war and has been sient（ever）since.
　　这只大钟在战争中损坏了，从此就一直不响了。
　　my uncle went to tibet in the 1950s. he has been living there（ever）since.
　　我叔叔五十年代就去了西藏，从那以后他一直生活在那里。
　　you have made great achievements in your work since graduation.
　　你们自毕业以来已经在工作中取得了巨大成就。
　　e．as soon as
　　as soon as...可译为一……就……，用来表示主从句的动作是紧接着发生的。
　　he will come and see you as soon as he can.
　　他一有空就来看你。
　　he rushed home as soon as he got the good news.
　　他一得到这个好消息就奔回家。
　　必背：
　　一……就……还可以用onupon doing 结构来表示。
　　on arriving home he called up lester.
　　= as soon as he arrived home, he called up lester.
　　他一到家就给莱斯特打电话。
　　f． immediately instantly directly
　　相当于as soon as，从句中用一般过去时态。
　　they phoned her immediately they reached home.
　　他一到家马上就给她打了电话。
　　i recognized her instantly i caught a glimpse of her.
　　我一看见她就把她认出来了。
　　we came directly we got your telephone.
　　我们一接到你的电话就赶来了。
　　g．the moment, the minute, the instant, the second
　　这几个名词短语也可用作连词，直接引导时间状语从句，表示一 就 。
　　he said he＂d turn on tv th moment he got home.
　　他说他一到家就打开电视机。
　　tell him i need to see him the minute he arrives.
　　告诉他，他一到我就要见他。
　　the second the bell rang, the students rushed out of the classroom.
　　铃一响，学生就冲出了教室。
　　h．hardly scarcely when , no sooner than
　　这两个短语都表示刚……就……，可以互换，主句通常用去完成时。
　　he had no sooner started out than he felt homesick.
　　他刚出发就想起家来。
　　he had hardly started his speech when someone rose to refute his points.
　　他刚开始发言，就有人站起来反驳他的论点。
　　注意：
　　当hardly, scarcely, no sooner
　　位于句子的开头时，主句须用倒装语序。
　　hardly had she fallen asleep when a knockat the door woke her up.
　　她刚要睡着，忽然敲门声把她吵醒。
　　no sooner was the frost off the ground than the work began.
　　地上的霜一消散，人们就开始工作了。
　　i．once
　　once作连词时，也相当于as soon as，但它含有的条件意味更浓，它引导的从句较短。
　　once you begin, you must continue.
　　一旦开了头，你就应当继续下去。
　　once you see him, you will neer forget him.
　　你一旦见过他，就不会忘了他的。
　　j．next time, the first time, the last time, every time 等
　　be sure to call on us next time you come to town.
　　下次你进城一定来看我们。
　　he left me a good impression the first time i met him.
　　我第一次见他时，他给我留下了好印象。
　　every time i see him he looks miserable.
　　我每次见到他，他都是一付痛苦的表情。
　　the last time i spoke to bob, he seemed happy enough.
　　上一次我见到他时，他看上去很开心。
　　k．by the time
　　by the tine 也可以引导时间状语从句，意为到 时为止，主句一般要用完成时态。
　　by the time he was fourteen, einstein had learned advanced mathematics all byhimself.
　　爱因斯坦到十四岁时就自学完了高等数学。 (从句为一般过去时，主句要用过去完成时)
　　i shall have finished my work by the time you return.
　　在你回来之前我将会做完我的活儿。(从句为一般现在时，主句要用将来完成时)
　　二、地点状语从句
　　地点状语从句通常由where, wherever（where的强势语）和everywhere引导，是表示空间关系的状语从句。
　　a．where
　　where 在……地方，去……地方
　　wuhan lies here the yangtze and the han river meet.
　　武汉位于长江和汉水汇合处。
　　where there is a will, there is a way.
　　有志者，事竟成。
　　i found my books where i had left them.
　　我的书在我原来放的地方找到了。
　　you＂d better make a mark where you have any questions.
　　哪儿有问题，你最好在哪儿做个记号。(这里where引导的从句不是定语从句)
　　注意：
　　在地点状语从句之前，不要使用介词。
　　【误】you should put the book at where it was.
　　【正】you should put the book where it was.
　　你应该把书放在原来的地方。
　　【误】we should go to where we are needed most.
　　【正】we should go where we are needed most.
　　我们应该到最需要我们的地方去。
　　b.wherever
　　wherevr在任何……地方，无论哪里
　　wherever you go, you should do your work well.
　　不论到什么地方，都要把工作做好。
　　you may sit down wherever you like.
　　你爱坐哪儿就坐哪儿。
　　c.everywhere
　　everywhere they went, they were kindly receivd.
　　他们每到一处都受到了友好的接待。
　　三、原因状语从句
　　原因状语从句是表示原因和理由的从句。引导原因状语从句的有as, because, since, now (that), considering that, seeing that等。
　　a．because
　　because因为
　　because i like it, i do it.
　　因为我喜欢，所以我才干。
　　he couldn＂thave seen me, because i was not there.
　　他不可能见过我，因为当时我不在那儿。
　　比较：
　　because 和for的区别。
　　1．for 是并列连词，只用于连接表示原因的分句，因此不能用于句首。because表示原因时，可位于句首。
　　【误】for he did not obey the rules, he was punished.
　　【正】because he did not obey the rules, he was punished.
　　由于他不遵守规章制度，他受到了处。
　　2．for 表示的是推断解释，because强调动作发生的直接原因。
　　it must have rained last night, for the ground is wet.
　　昨晚肯定下雨了，因为地面是湿的。（不可用because，因为地面湿不是天下雨的原因）
　　the day breaks, for the birds are singing.
　　天亮了，因为鸟在叫。（不可用because，因为鸟叫不是天亮的原因）
　　he went to bed early, because he was tired
　　由于他累了，所以他很早就上了床。（直接的理由）
　　he must be tired, for he went to bed early.
　　他肯定累了，因为他很早就上了床。（间接的推断）
　　3．在强调结构it iswas that和关联词not but 引导的原因状语从句中，宜用because。
　　it＂s because he helped you that i＂m prepared to help him.
　　正是因为他帮助过你，所以我乐意去帮助他。
　　he decided to give up thechance of going abroad, not because he did not want
　　to but because his wife was ill.
　　他决定放弃出国的机会，不是因为他不想去，而是因为他妻子病了。
　　b．since
　　since 因为，既然。引导的从句大多置于句首，主从句的时态一般相同。
　　since you have no licence, you are not allowed to drive.
　　因为你没有驾驶执照，所以不允许你开车。
　　since you are al here, let＂s try and reach a decision.
　　既然大家都来了，咱们就设法做出一个决定吧。
　　c．as
　　as 由于。一般多用于句首。
　　as she was ill, she didn＂t come to the party.
　　由于病了，她没来参加晚会。
　　as he was not well enough, i had to go without him.
　　由于他身体欠佳，我只好不带他去了。
　　as it rained, we all stayed at home.
　　由于下雨我们都呆在家里。
　　c．because, since, as 的区别
　　1．because语气最强，表达的是未知的新信息，一般置于主句之后，也可以放在主句之前，用逗号隔开。在回答why引导的特殊疑问句时，或在强调结构it iswas  that 和关联词not  but 引导的原因状语从句中，要用because。另外，because还常和副词just, merely等连用。
　　2．since 往往表示的是已知的客观事实，或分析后的推理，引导的从句大多置于句首，主从句的时态一般相同。
　　3．as 表示的理由最弱，只是对主句的附带说明，重点在主句。as从句通常放在主句前。
　　just because he doesn＂t complain, you must not suppose that he is satisfied.
　　你不可只因他不抱怨就以为他满足了。
　　you shouldn＂t get angry only because some people speak ill of you.
　　你不该仅仅因为有些人说了你的坏话就生气。
　　since you＂re not interested, iwon＂t tell you about it.
　　既然你不感兴趣，那我就不告诉你了。
　　as you are unable to answer perhaps we should ask someone else.
　　因为你不能回答，也许我们该问一问别的人。
　　注意：
　　because等词不能与 so连用。
　　【误】because he was careless, so he failed in the exam.
　　【正】because he was careless, he failed in the exa.
　　由于他粗心，所以他考试不及格。
　　【正】he was careless, so he failed in the exam.
　　由于他粗心，所以他考试不及格。
　　e．now that
　　now that 既然，因为。that可以省略。
　　now (that) dinner is ready, go and wash your hands.
　　既然饭已好了，洗手去吧。
　　now you mention it again, i do remember.
　　既然你又提起此事，我倒回想起来了。
　　f．conidering that, seeing that
　　这两个词和since, now that意思相近，都有鉴于 事实，考虑到 的意思。
　　seeing that quite a few people were absent, we decided to put the meeting off.
　　由于好些人都没到会，我们决定延期开会。(seeing 后面的that可以省略)
　　considering that they are just beginners, they are doing quite good job.
　　考虑到他们才刚刚学做，他们干得算很不错的了。
　　g．not that   but that
　　这一结构相当于汉语的不是因为 而是因为。
　　not that i don＂t like the film, but that i have no time for it.
　　不是因我不喜欢看这部电影，而是因为我没有时间看。
　　状语从句（二）
　　四、目的状语从句
　　目的状语从句是表示行为目的的从句。引导目的状语从句的主要连词有that, so，so that, so that, in order that等，从句中常常使用一些情态动词，如can, could, may, might, should等。a．that, so that，in order that表示为了，以便，一般放在主句之后。that语气较弱，用的较少，多用so that。let＂s take the front seats that we may se more clearly.
　　我们坐前排吧，这样我们可以看得更清楚些。
　　man does not live that he may eat, but eats that he may live.
　　人生存不是为了吃饭，而吃饭是为了生存。
　　they hurried so that they might not miss the train.
　　他们为了不误火车，才急急忙忙的。
　　in order that everyone present might hear her clearly, she raised her voice again.
　　为了使在场的每个人都能听清楚，她再次提高了声音。
　　注意：当主从句的主语一致时，so that和in order that引导的目的状语从句可以转换成相对应的动词不定式结构。
　　we got upearly so that we would arrive in time.
　　为了能及时赶到，我们起得很早。
　　they hurried so that they might not miss the train.
　　they hurried so as not to miss the train.
　　他们为了不误火车，才急急忙忙的。
　　betty saved money in order that she could uy a portable computer.
　　betty saved money in order to buy a portable computer.
　　贝蒂存钱是为了买一台手提电脑。
　　b．in case, lest, for fear that
　　几个短语都表示万一，惟恐，含有否定的意义。
　　better take more clothes in case the weather is cold.
　　最好多带些衣服以防天气会冷。
　　take an umbrella in caseit rains.
　　以防下雨，带把伞。
　　五、结果状语从句
　　结果状语从句是表示事态结果的从句。引导结果状语从句的连词有：that, so (that), so that, such that等。结果状语从句通常置于主句之后。
　　a．so, that, so that
　　这三个词都可以引导结果状语从句。so that最为常用，so或that常用于口语或非正式文体中。
　　what has happened tha you look so worried
　　发生了什幺事，使你显得如此担心？
　　i didn＂t plan the work well, so thatso i didn＂t finish it in time.
　　我没把工作计划好，结果没按时完成。（so that从句常用逗号与主句隔开）
　　the room was packed with people, so that we couldn＂t get in.
　　房间里挤满了人，我们进不去。
　　c．so...that so...that 如此……以致……。其引导的果状语从句有如下四种结构：
　　1．so + 形容词副词 + that-从句
　　the village is so small that it cannot be shown in the map.
　　这村子太小，所以这地图上没有。
　　the wind was so strong that we could hardly move forward.
　　风刮得那么大，我们简直寸步难行。
　　2．so + 形容词 + aan + 单数名词 + that-从句it was so hot a day that tey all went swimming.
　　天是那么的热以致他们都去游泳了。
　　he made so inspiring a speech that everybody got excited.
　　他发表了如此鼓舞人的演讲以致大家都很激动。
　　3．so + manyfew +复数名词+ that-从句i have had so many falls that i am black and blue all over.
　　我摔了许多跤，以至于浑身青一块，紫一块。
　　he has so few friend that he often feels lonely.
　　他朋友很少，所以经常感到孤独。
　　4．so + muchlittle +不可数名词 + that-从句
　　i had so little money then that i couldn＂t even afford a used car.
　　我当时囊中羞涩，甚至连一辆二手车都买不起。
　　he drank so much wine last night that he felt terrible.
　　昨晚他喝了那么多的酒，他觉得很不舒服。
　　5.在so + 形容词副词 + that-从句结构中，如将so + 形容词副词位于句首，主谓语要倒装。
　　so excited was he that she could not say a word.
　　他很激动，一句话都说不出来。
　　so loudly did he speak that even the people in the next room could hear him.
　　他说得很响，连隔壁的人都能听见。
　　d．such... that such...that 如此……以致……。其引导的结果语从句有如下四种结构：
　　1．such + aan + 形容词 + 单数可数名词 + that-从句
　　jenny is such a clever girl that all of us like her very much.
　　詹妮是如此聪明的女孩，以至我们都非常喜欢她。
　　we left in such a hurry that we forgot to lock the door.
　　我们走得匆忙，把门都忘了锁了。
　　2．such + 形容词 +复数名词+ that-从句
　　he gave suchimportant reasons that he was excused.
　　他说出了这么重要的理由，得到大家的谅解。
　　they are such interesting novels that all of us want to read them.
　　这些是十分有意思的小说，大家都想看。
　　3．such + 形容词 + 不可数名词 + that-从句
　　he made such rapid progress that the teacher praised him.
　　他的进步很快，老师表扬了他。
　　h shut the window with such force that the glass broke.
　　他关窗子用了那么大的劲，玻璃都碎了。
　　提示：such+aan+形容词+单数名词结构可以和so +形容词+aan+单数名词结构互换。
　　he told us such a funny story that we all laughed.
　　he told us so funny a story that we all laughed.
　　他给我们讲了一个如此有趣的故事，大家都笑。
　　the story he told us was so funny that we all laughed.
　　他给我们讲的故事是如此有趣，大家都笑了。
　　e．such that
　　such that可以连用，意思是（是）这样...以致。
　　mother＂s answer was such that she didn＂t say yes and she didn＂t say no.
　　妈妈的回答就是这样，既没有同意也没有不同意。
　　his anger was such that he lost control of himself.
　　他勃大怒，以致不能自制。
　　比较：such ...that ... 引导的是结果状语从句。
　　such ...as ...引导的是定语从句（请参考第10章定语从句）。
　　she had such a fright that she fainted.
　　她吓得昏了过去。
　　luckily such earthquakes as can cause a lot of damage do no happen very often.
　　很幸运，这种破坏性很大的地震并不经常发生。（关系代词as在定语从句中作主语）
　　六、条件状语从句。
　　条件状语从句是表示主句动作发生的前提或条件的从句。条件状语从句分为真实条件状语从句和非真实条件状语从句（见第3章）。引导条件状语从句的有if, unless, so as long as, as so far as, on condition that, in case, suppose, supposing等。条件状语从句中的谓语动词一般要用现在时或过去时代替一般将来时或过去将来时。
　　a．if if表示正面条件，意为如果。
　　if you ask hm, he will help you.
　　如果你向他请求，他会帮助你。
　　difficulties are nothing if we are not afraid of them.
　　如果我们不怕困难，困难就算不了什么了。
　　if i do not understand what he says, i always ask him.
　　我不懂他的话时, 总是去问他。（if = when）
　　比较：
　　if only和only if的对比。
　　if only 解释但愿，要是 就好了，表示一个不可能实现愿望，要用虚拟语气。
　　only if 解释只有，等于only on condition that，从句用陈述语气。
　　only if you heat ice, it turns to water.
　　只有当你给冰加热，它才会变成水。
　　if only i knew!
　　要是我知道该多好。
　　b．unless
　　unless = if not, 表示反面条件，意思是如果不、除非。
　　they will go tomorrow unless it rains.
　　除非明天下雨，否则他们会去的。
　　（they will go tomorrow if it doesn＂t rain.）
　　i won＂t let you in unless you show me your pass.
　　如果你不出示通行证，我就不让你进来。
　　（= i won＂t let you in if you don＂t show me your pass. ）
　　注意：
　　if...not和unless通常是可以换用的。但在下列情况下，两者是有区别的：
　　1．unless多引导真实条件句，if not可以引导真实条件句或非真实条件句。
　　hewon＂t be able to pass the final exams unless he works hard.
　　除非他努力，否则就通过不了期末考试。
　　he won＂t be able to pass the final exams if he doesn＂t work hard.
　　如果他不努力，就通过不了期末考试。
　　he would pass the final exams if he worked hard.
　　要是他努力的话，他就会通过考试。（非真实条件句。含义是he doesn＂twork hard.）
　　2．如果主句描述的是情感或情绪活动方面的内容，if not结构不能换成unless。如：
　　i＂ll be quite glad if she doesn＂t come this evening.
　　她今晚如果不来我很高兴。
　　3．unless引导的状语从句可用否定结构，而if not引导的从句不可再用否定结构。
　　don＂t ask me to explain again unless you really don＂t understand.
　　不要再叫我解释了，除非你真的不懂。
　　4．uless能作为介词使用，相当于except，而if not不可以。
　　nothing will come out of it unless disaster.
　　这种事除非引起灾祸之外不会有什么结果。
　　c．so long as, as long as, on condition that
　　这几个短语意思差不多，都表示只要，条件是……。
　　asso long as we don＂t lose heart, we＂ll find a way to overcome the difficulty.
　　只要我们灰心，我们就能找到克服困难的方法。
　　you may use the room on condition that so long as you clean it afterwards.
　　只要你用完后打扫干净，你就可以使用这个房间。
　　d．in case
　　in case 既引导目的状语从句，也可以引导条件状语从句，等于if it happens that。
　　in case i forget, please remind me of my promise.
　　如果我忘了，请提醒我所做的承诺。
　　send s a message in case you have any difficulty.
　　万一你有什么困难，请给我们一个信儿。
　　e．providing, provided that, supposing, suppose that, given that
　　这几个短语意思相近，有如果，只要，假如等意思。
　　given that they are inexperienced, they＂ve done a good job.
　　考虑到他们缺乏经验，他们的工作已做得很好了。(that可以省略)
　　rovided providing（that）we invite him, he would surely come to dinner.
　　假如我们邀请他的话，他肯定会来吃饭的。
　　supposesupposing we can＂t get enough food, what shall we do
　　假设我们弄不到足够的食物，那我们怎幺办？（仅用于疑问句）
　　七、方式状语从句
　　方式状语从句是描述动作方式的从句。方式状语从句常由as, as if as though等词引导，通常位于主句之。
　　a．as, just as
　　这两个连词的意思是如……，正如……一样。just as 比as 语气要强一些。
　　do in rome as the romans do.
　　入乡随俗。
　　leave things as they are.
　　让一切顺其自然。
　　please do as you are told.
　　请按照人家告诉你做的去做。（也可说please do as told.）
　　balloons float in the air just as boats do on the sea.
　　气球在空中就如同船浮在海面上一样。
　　注意：
　　在口语中，还可用like来代替as，引导一个方式状语从句。
　　she is doing the work exactly like i want her to.
　　她正在完全按照我要她的那样在做这项工作。
　　do you make bread like you make cakes
　　你做面包的方法是不是和做点心一样？
　　b．as if, as though
　　由as if 或as though引导的状语从句可以用陈述语气表示可能符合事实的情况，也可以用虚拟语气的过去式表示现在不符的或与事实相反的情况（见第3章虚拟语气）。
　　she looks as if she is ill.
　　看上去她好象是生病了。
　　the boy plays piano as though he has a natural ear for music.
　　这孩子弹起钢琴来家好象天生很懂音乐似的。
　　they talked loudly as if nobody were around.
　　他们大声说话仿佛周围没人似的。
　　he acted as ifthough nothing had happened
　　他装得似乎什么事也未发生过。
　　八、比较状语从句
　　比较状语从句由as, than引导。
　　a．as...as, the same as
　　用于同等程度级的比较。否定句用not soas   as, not the same  as。
　　our country is as big as the whole of europe.
　　我们的国同整个欧洲一样大。
　　the result was not asso good as i had expected.
　　结果不如我预料的那么好。
　　she works in the same building as my sister.
　　她和我的妹妹在同一大楼上班。
　　b．than
　　than表示不同程度级的比较
　　it rains mor often in shanghai than in beijing.
　　上海下的雨比北京的多。
　　he is two inches taller than his father.
　　= he is taller than his father by two inches.
　　他比他爸爸高两英寸。
　　注意：
　　在比较从句中通常把和主句重复的部分省掉，如果把省略部分补上，而显得累赘或不合乎习惯。
　　lily isn＂t so clever a girl as lucy is.
　　莉莉是一个不如露西那样聪明的女孩。（如说成：lily isn＂t so clever a girl as lucy is clever 显得累赘）
　　the child sang as sweetly as a nightingale.
　　这孩子歌唱得同夜莺般婉转。
　　c．the more..., the more...
　　这是表示比例的比较，意思是越……就越……。第一个the more 也可以看成是一个条件。
　　the more you read, the better you understand.
　　你看的书越多，你懂得就越多。（= if you read more, you will understand better.）
　　the busier he is, the happier he feels.
　　他越忙越开心。
　　the more difficult the questions are, the less likely i am to be able to answer them.
　　问题越困难，我就越可能回答。
　　必背：
　　一些常见的倍数比较句型。
　　his father is double twice his age.
　　他爸爸的年龄是他的两倍。
　　his father is twice double as old as he (is).
　　他爸爸的年龄是他的两倍。
　　our new school is three times bigger than the old one.
　　我们的新学校比老学校大三倍。
　　our new school is four times as big as the old ne.
　　我们的新学校是老学校的四倍大。
　　our new school is four times the size of the old one.
　　我们的新学校是老学校的四倍。
　　九、让步状语从句
　　让步状语从句表示在某种相反的条件下，主句中的情况依然会出现。让步状语从句由although, though, however, whatever, whoever, whomever, whichever, whenever, wherever, whether（是否）, no matter (who, wha, etc), even if, even though等词引导。
　　a．although, though
　　这两个词意思一样，都解释虽然，尽管。although比though正式。
　　1．although指事实，多用于句首。多数情况下可与though换用。
　　although he is young, he is very clever.
　　他尽管年轻，但很聪明。
　　although his illness had prevented him from studying, he managed to pas the exam.
　　尽管病情妨碍了他学习，但他还是通过了考试。
　　it was an exciting game, although no goals were scored.
　　那是一场精彩的球赛，尽管一个球都没进。（although也可放在主句之后）
　　2．though既指事实，又指设想。可用于句首、句中或句末。
　　though he is poor, he is happy.
　　他虽然穷，但很快乐。
　　i haven＂t checked the information yet, though i thik it is correct.
　　我还没有核实这份资料，但我认为它错不了。
　　my house, though it is large, is also made of stone and wood.
　　我的房子虽然大，但是也是用石头和木料搭成的。
　　提示：
　　有时though= and yet但是，然而，放在句子末尾，前面用逗号。
　　it was hard work; i enjoyed it, though.
　　那工作很苦，但是我喜欢干。
　　（= it was hard work, but i enjoyed it.）
　　3．hough从句有时可以倒装，将从句中的一部分提置句首。（详见第13章）
　　child though he is, he knows a lot.
　　尽管他是个孩子，他懂得的东西却很多。
　　（=although he is a child, he knows a lot.）
　　strange though it may look, it is true.
　　尽管看起来奇怪，但是却是真的。
　　(= though it looks strange, it is true.)
　　注意：
　　although, though不能与ut连用，但是可以与yet, still, nevertheless连用。
　　although though he blames me, yet i will trust him.
　　尽管他责怪我，但我还是愿意信任他。
　　though he was hungry, still he would not eat.
　　尽管他饿了，但是他仍然不想吃。
　　b．even if, even though
　　这两个词语气比though, although强，解释即使，两者可以通用。
　　we won＂t be discourged even if though we fail ten times.
　　我们就是失败十次也不泄气。
　　even if though you fail, you will have gained experience.
　　纵然你失败，你也会得到一些经验。
　　c．while, whereas
　　这两个词也可引导让步状语从句，突出主句和从句的对比。
　　while i understand what you say, i can＂t agree with you.
　　虽然我理解你的意思，但我还是不同意。
　　some people like fat meat, whereas others hate it.
　　有些人喜欢肥肉，相反有些人讨厌肥肉。
　　d．no matter (who, what, where, when, etc)
　　这几个词引导的让步状语从句语气十分强烈。
　　this is not true, no matter who says so.
　　不管谁这么说，都不对。
　　do it no matter what others say.
　　不管别人怎么说，尽管干。
　　no matter how bus he was, he studied english every day.
　　不管他多忙，他都每天坚持学习英语。
　　e．however, whatever, whenever, wherever
　　这些词在意思上和用法上都等于no matter how what
　　whatever happens may happen, we shall never lose hope.
　　无论发生什么，我们都不要失去信心。（有时从句中的动词与may连用）
　　however (=no matter how) expesive it may be, i＂ll take it.
　　无论它有多贵，我也要买下它。
　　don＂t let them in, whoever (=no matter who) they are.
　　不管他们是谁，别让他们进来。
　　f．whether...or (not) ...
　　whether...or (not) ...意思是不管……还是……。
　　whether you believe it or not, it＂s true. 不管你信不信，这是真的。
　　whether the weather is good orbad, they will set off as planned.
　　不管天气是好还是坏，他们都要按计划启程。
　　提示：
　　也可直接用or来连接两个相同结构来表示让步。
　　walking or sleeping, she always has the question in her mind.
　　无论走路还是睡觉，她总是想着这个问题。
　　g．as
　　连词as，同though一样，也可以引导让步状语从句，但从句中要用特殊语序。
　　young as he is, he knows a lot.
　　他虽然年轻，但懂得很多。(= though he is young, he .)
　　cold as it is, the children play outdoors.
　　虽然天气冷，但孩子们仍在户外玩。
　　h．if
　　if 有时也可用于让步状语从句，相当于even if。
　　if he is por, he is at least honest.
　　尽管他穷，但至少他很诚实。
　　we＂ll go if it rains.
　　即使下雨我们也要去。
　　i＂ll do it if i die in the attempt.
　　即使会丧命我也要试一下。
　　注意：
　　有些时间、地点、条件、方式或让步等状语从句中，如果谓语含有动词be，主语又和主句中的主语一致，或者主语是it，常把从句中的主语和谓语的一部分（特别是动词be）省略掉。
　　look out for cars when crossing the stret.
　　过街时当心车辆。
　　(= when you are crossing the street)
　　she hurriedly left the room as though angry.
　　她急匆匆地走出屋去，好象很生气的样子。
　　(= as thoughif she was were angry )
　　if possible, i＂d like to have two copies of it.
　　可能的话，我想要两本。(= if it is possible, )
　　she advised me not o say anything unless asked.
　　她劝我别说什么，除非有人要我说。
　　(= unless i was asked )
　　as a young man, he studied law and became a lawyer.
　　他年轻时就学了法律，并当了律师。
　　(= as when he was a young man, )