英语语法专项之状语从句1.时间状语从句2.条件状语从句3.原因状语从句4.结果状语从句5.比较状语从句6.目的状语从句7.让步状语从句8.地点状语从句用来修饰主句中的动词，副词和形容词的从句叫状语从句。
根据其含义状语从句可分为时间状语从句，地点状语从句，条件状语从句，原因状语从句，结果状语从句，比较状语从句，目的状语从句，让步状语从句。
各类状语从句连接词（短语）一览表：时间when, while, as, as soon as, since, until, after, before ，as long as（长达……之久）条件If, unless,as/so long as（只要）原因As, because, since ，as/so long as（既然,因为）地点Where目的So that（为了）, in order that结果So that （方便）, so… that, such … that 让步though, although, even if, however 方式As比较than, （not）as … as1.时间状语从句时间状语从句常见的从属连词有：（注意其汉语意义）when, while, as, before, after, since, until （till） once as soon as, the moment, the minute, immediately, directly, each/every time, the first time, the last time, next time, by the time, whenever 等。
例如：Every/Each time I was in trouble, he would come to my help.I thought her nice and honest the first time I met her. 注意：（1）when, while,as 的区别：1）when 引导从句时，主从句的动作有先有后，也可以同时进行,从句的动作可以是持续性的，也可以是短暂的。
如：When I got to the airport, the plane had already taken off. （主先从后）（短暂性）When I lived there, I used to go to the seaside on Sundays. （同时）（持续性）When the movie ended, the people went back. （从先主后）2）while 侧重主从句动作的对比，且从句的动词必须是持续性的。
如：While we were chatting she was looking at the time table on the wall．3）as 引导从句时侧重主从句动作同时或几乎同时进行，从句的动作可以是持续性的，也可以是短暂的。
如：Sometimes I watch TV as I am having breakfast．4）when 和while 还可以是并列连词，意思分别是“就在这时”，“然而”。
如：I was having a rest on the sofa when the telephone rang．They were surprised that a child should work out the problem while they couldn' t .注：并列连词when 常用与以下句型中：①…was/were doing…when…（正在做…突然）②…was/were about to do…when…（刚要做…突然）③…was/were on the point of doing…when…（刚要做…突然）④…had justdone…when….（刚一…就）⑤Hardly/Scarcely had…done…when…（刚一…就）（2）before 引导从句时,词义非常灵活，注意下列句子中的before 的词义：1.Before I could get in a word, the tailor had measured me.（还没来得及…就）2.We hadn't run a mile before he felt tired.（还没…就）3.We had sailed 4 days before we saw land.（…才…）4.Please write it down before you forget it.（趁还…没就）（3）till （until）和not…till （until）1）till （until）:主句谓语动词必须是持续性的，意思是“到…为止“如：He remained there till/until she arrived.2）not…till （until）…: 主句谓语动词必须是短暂性的，意思是“直到…才” 如：She won't go to bed till/until he returns home.3）not…until 还有强调式和倒装式：强调句：It is not until he returnshome that she will go to bed. 倒装句：Not until he returns home will she go to bed.（4）几个极易混淆的时间状语从句：1）It was +时间点+when…（当的时候时间是）It was 5 am when we arrived at the village.2）It was/will be+时间段+before…（没过…就／过了…才）It was/will be two weeks before we met/meet again.3）It is /has been +时间段+since…（自从…以来有…）It is/has been 3 years since we last met. 突破点：一看be 动词的时态，二看时间段还是时间点。
注意：在“It is /has been +时间段+since…”句型中，从句的动词必须是短暂性的，如果是延续性的动词，时间要从从句的动作结束时算起。
如：It is 3 years since I smoked.（我戒烟有三年了）补充：as soon as, immediately, directly, instantly, the moment, the minute, the instant, no so oner…than…, hardly/scarcely….when….和once 这些从属连接词引导的从句都表示从句的动作一发生，主句的动作随即就发生，常译为“一…就…”。
从句中一般时态代替将来时态。
every time, each time, next time, the first time, any time, all the time等名词短语用来引导时间状语从句，表示“每当…..，每次…..；下次……”等。
1. It was quiet those big trucks started coming through the town.A. beforeB. afterC. untilD. unless2.It seemed only seconds _______ the boy finished washing his face.A. whenB. beforeC. afterD. even if3.Hardly had he reached the school gate ______ the bell rang.A. whileB. whenC. asD. as soon as4.________________________________________ We were told that we should follow the main road ___________________________ we reached the centra l railway station. A. whenever B. until C. while D. wherever5.I recognized you _______ I saw you at the airport.A. the momentB. whileC. afterD. once6.He was about to go to bed _______ the doorbell rang.A. whileB. asC. beforeD. when7.______ I listen to your advice, I get into trouble.A. Every timeB. WhenC. WhileD. Until8.__ John was watching TV, his wife was cooking.A. AsB. As soon asC. WhileD. Till9.The children ran away from the orchard（果园） they saw the guard. A. the moment B. after C. before D. as10.No sooner had I arrived home ___ it began to rain.A. whenB. whileC. asD. than11.Several weeks had gone by ___ I realized the painting was missing.A. asB. beforeC. sinceD. when12.It __ long before we ____ the result of the experiment.A. will not be; will knowB. is; will knowC. will not be knowD. is; know 13.–What was the party like?--Wonderful. It's years ____ I enjoyed myself so much.A. afterB. beforeC. whenD. since14.The new secretary is supposed to report to the manager as soon as she ___ .A. will arriveB. arrivesC. is going to arriveD. is arriving15.__ got into the room ___ the telephone rang.A. He hardly had; thenB. Hardly had he; whenC.He had not; thenD. Not had he; when16.No sooner had he finished his talk ___ he was surrounded by the workers.A. asB. thenC. thanD. when17.–Did you remember to give Mary the money you owed her? --Yes, I gave it t o her I saw her.A. whileB. the momentC. suddenlyD. once18.I thought her nice and honest ___ I met her.A. first timeB. for the first timeC. the first timeD. by the first time19.He will have learned English for eight years by the time he __ from the u niversity next year.A. will graduateB. will have graduatedC. graduatesD. is to graduate20.The moment the 28th Olympic Games ___ open, the whole world cheered.A. declaredB. have been declaredC. have declaredD. were declared答案：CBBBA DACAD BCDBB CBCCD2.条件状语从句条件状语从句引导词：if（如果） ,unless（除非）, incase（以防）时态：主将从现（可能会发生的事情）主现从现（肯定会发生/祈使句）1.if 引导的条件状语从句，可位于前面或后面，但是如果放在后面，主从句用逗号隔开。