高一英语语法知识（6）状语从句(1)时间状语从句、原因状语从句状语从句主要用来修饰主句或主句的谓语。一般可分为九大类，分别表示时间、地点、原因、目的、结果、条件、让步、比较和方式。一、时间状语从句1、when, while, as 引导时间状语从句1).when(at or during the time that) 只表示一般的时间关系，它既可指时间的一点(a point of time)，也可指一段时间(a period of time)。用when时，从句的动作可与主句的动作同时发生，也可先于主句的动作，因此when用得最多。When the clock struck twelve, all the lights went out.Dont forget to return this book for me, when you go to the library.2).while(during the time that) 只能指一段时间，而不能指一点时间。用while时，从句的动作或者与主句的动作同时发生，或者主句的动作是在从句的动作的进展过程中发生的。因此，从句中的谓语必须是表示延续性动作或状态的动词。这是while与when的主要差别。Strike while the iron is hot. Please dont talk so loud while people are working.3). as (at the same moment that) 往往可与when通用，但它着重指从句与主句的动作相伴随发生，可译成：一面一面，表示随着时，as用得较多。Kate read the book as she went along. We took notes as we listened to the lecture.As it became more common for women to work outside the house, men began to share the housework. 随着妇女就业普遍了，男职工分担了家务劳动。注意：1).在用when和while连接的从句中，常省略与主句相同的主语和相应的be，而在as连接的从句中一般则不省略。Wood gives much smoke while (it is) burning.He fell asleep while (he was) studying his grammar book.While in London, he studied music. When (they are) heated, metals expand.2).when和while还可作并列连词用：A. when做连词引导并列句,译为“这时”，表示同时，前面有逗号，不能用while代替。所构成的并列句句型有：was/were about to do whenwas/were on ones way whenwas/were on the point of doingwhen 刚好做某事这时was/were doing when 正好做某事这时had done when 刚好做完某事这时Joan was holidaying with her family in a wildlife park when she was bitten on the leg by a lion.I was about to go to bed when the telephone rang.B. while 做连词引导并列句,译为“而”表示对比。I like singing while she likes dancing.2. as soon as “一就” 引导时间状语从句,类似意思的连词还有九个，分三组： the moment immediately No sooner .thanthe minute directly Hardly.whenthe instant instantly Scarcely . when.u 第一组：the+名词the moment/ the minute/ the instantu 第二组：ly 形式immediately/ directly/ instantlyu 第三组 倒装句/ No soonerthan/Hardlywhen/ ScarcelywhenThe moment she comes, Ill call you. She left here immediately the clock struck 12.Hardly had he got off the bus when he heard a loud noise.提醒同学们Hardly . when ./ No sooner. than./ Scarcely.when.主句用过去完成时，从句用一般过去时。3. before/after引导时间状语从句, 此处重点注意before的用法：1)“还没等”谓语不用否定式。Before they got to the bus stop, the bus had gone。2）当before引导的从句位于主句之后，译成“才/就”，It was evening before we reached the little town of Winchester.到了晚上我们才到达Winchester小镇。3）“趁着还没”Lets leave here before it is dark.固定句型：It will (not) be some time before do It was (not) some time beforedidIt wont be long beforedo It wasnt long beforedid4. until/till （till 不用于句首及强调句），引导时间状语从句1).not.until/till. 直到才，主句谓语是终止性动词用否定式。He didnt go to bed until he had finished his work.2).until/till.直到.为止，主句谓语是延续性动词用肯定式。We were told that we should follow the main road until we reached the central railway station.3) It is not untilthat.强调句式It was not until midnight that he went back home after the experiment.4)Not until放在句首时，主句倒装。Not until he came close to me did I recognize him.5.since引导时间状语从句，主句要用完成时1)主句（现在完成时）.ever since.状从（过去时）译为”自从”Mr Li has been here ever since he came back. 2)It is (has been) +段时间. since.状从（过去时） It was +段时间.since.状从（过去完成时）since后用的动词不同，动作的起算时间不同：since终止性动词的过去式，从该动作发生时算起since+延续性动词的过去式，从该动作结束时算起或译成否定意思。It is five years since they married. It is over ten years since he worked here.6. 引导时间状语从句的还有： the first time each time by the time the last time every time the next time其中by the time句型有时态的要求。By the time +状从（过去时），主句（过去完成时）By the time +状从（现在时），主句（将来完成时）Each time he came to my city, he would call on me.By the time she came back, all the guests had left.By the time the class is over, we will have learned the whole passage.7. 注意：1）主句与时间状语从句的时态原则是主将从现Will you please bring me your book when you come here tomorrow?二原因状语从句1.引导原因状语从句的从属连词主要有because, as, since，seeing (that), now (that), considering (that)，in that等：1) because 译为 “因为”用来回答why的提问，表示直接原因，语气强烈 ，强调原因状语从句可用在强调句中，着重点在从句， It was because he was ill that he did not go with us. In that he is ill, he feels unable to do it.2) since 译为 “既然”，“鉴于”， since 的语气比because弱。表示关系上的明显原因，特别用于对方已经清楚的事情，无须要加以说明的既成事实的理由，全句中心在主句。Since you have got a chance, you might as well make full use of it. 3) as 译为“由于” 语气最弱，表示附带说明的“双方已知的原因”，说明一般的因果关系，全句中心在主句（即可于句首，也可于句中）。As he didnt know much English, he and looked up the word “cough” in the dictionary.4）now that/seeing that/considering that 译为 “既然”用来说明一种新情况，然后加以推论，于(句首), that可省。Now (that) everyone is ready, lets have our competition.Seeing (that) its raining, wed better stay indoors.Considering (that) everybody is here, lets begin our discussion.注意:1) for引导的原因状语，属于并列句，而不是状语从句，只能放在句中连接两个并列句。通常for引导的并列句，前一分句表示推测意思，后句话是补充说明前句的。for引导的句子只