初中英语语法大全——状语从句在句中起状语作用的从句叫作状语从句。
状语从句可以位于句前、向中成向居。
位于句首时，常用迅号与主句隔开，位于句中时以句前后须用过号，位于句居时，从句的前面可以不用逗号。
状语从句主要包括时间状语从句地点状语从句、条件状语从句、原因状语从句、目的状语从句、结果状语从句、让步状语从句方式状语从句和比较状语从句。
一、时间状语从句引导时间状语从句的从属连词主要有when( ..时候)，while( ...时候),as( ...时候), before(在...之前),after(在....之后)，until/till（直到......），... since( ...以来),as soon as(一.......就......）等。
在时间状语从句中，要注意时态一致。
1.when, while和as的用法(1) when, while和as的共同用法when, while和as都可以引导时间状语从句，意为“当......时候”。
若表示主何中的动词和从句中的动作同时发生，而从句的谓语动词是延续性动词时，这三个词是等同的，可以互换。
eg: When/While/As we were dancing, a stranger came in. 当我们跳舞的时候，一个陌生人进来了。
eg: When/While/As I was taking a bath, the telephone rang. 我在洗澡的时候，电话响了。
(2) when, while和as的用法区别①when引导的时间状语从句的谓语动词既可以是延续性的,也可以是非延续性的，而while引导的时间状语从句的谓语动词只能是延续性的。
eg: When you came in, I was talking with a few boys. 你进来时，我正在和几个男孩子谈话。
eg: While we were waiting for the bus, it was raining heavily. 我们等公交车时，天正下着大雨。
②while和as常表示从句的动作与主句的动作同时发生，而when表示从句的动作发生在主句的动作之前、之后，也可同时发生。
eg: They rushed in while/as we were discussing problems. 当我们正在讨论问题时，他们冲了进来。
eg: When he had finished his homework, he took a short rest. 他写完作业后，休息了一会儿。
eg: When I got to the airport, the guests had left. 当我到达机场时,客人们已经离开了。
③while表示两个延续性动作同时发生而又有对比意义，主从句的时态通常是相同的。
eg: While she was making a phone call, I was writing a letter. 她打电话时,我正在写信。
eg: Eddie was sleeping while Millie was reading a magazine. 艾迪在睡觉而米莉在看杂志。
④as意为“随..... .... 边....”常用于表示两个动作同时或者几乎同时发生;表示两个发展变化中的情况;表示在某事发生的过程中另外一一件事发生;表示随着短暂动作的发生，另一动作立刻发生。
eg: As you older, you will know better and better about yourself. 随着年龄的增长，你会越来越了解自己。
eg: As he was reading , he was shaking his head. 他边读书边摇头。
2. as soon as的用法as soon as意为“一....就 ...”，表示从句的动作一发生，主句的动作随即发生。
eg: Mom, I'm leaving for Beijing tomorrow. --- That's nice. You'd better ring me up as soon as you get there. 妈妈，明天我将去北京。
--- 那很好。
你最好一到那里就给我打个电话。
eg: As soon as he heard the news, he jumped with joy. 一听到这个消息，他高兴地跳了起来。
2.since的用法(1) since意为“自从....”, 主句常用现在完成时或般现在时，从句常用一般过去时。
eg: I have lived in England since I was three. 自3岁起我就一直住在英国。
eg: It is two years since I became a college student. 我成为一名大学生已经两年了。
(2) 从句谓语不同，表达的意义不同。
① since引导的从句的谓语如果是延续性动词成者表示状态的动词，则从句表示的时间是从该动作或状态结束时算起。
eg: It has been a year since he worked here. 他不在这里工作已经一年了。
eg: He has written to me regularly since he was ill.自从病好以来，他定期给我来信。
② since引导的从句的谓语如果是延续性动词，则从句表示的时间是从该动作开始的那刻算起。
eg: We haven't seen each other since we parted. 自从分手以后我们一直没有见过面。
eg: We have been good friends since we joined the team. 自从加入这个队以来,我们就成了好朋友。
③ It is/has been..since句式“It is/has been+时间段since从句”句式表示“自...以来有(多久)”。
since从句不可以用否定句。
eg: It is has been 5 years since we last met. 自从我们上次见面以来已经有5年了。
eg: It has been a long time sine Mary was ill. 玛丽病好很长时间了。
④ until /till的用法until/till意为“直到....为止”。
当主句为否定句时，常构成“not...until...”结构，意为“直到......才......”(1) 主句是否定句时主句如果是否定句,谓语动词需用非延续性动词，表示主句的云作到从句表示的时间点才开始。
eg: You can't leave until you have finished your homework. 家庭作业写完后你才能离开。
eg: I didn't know anything about it until you told me. 直到你告诉我，我才知道关于这件事情的一切。
(2)主句是肯定句时主句如果是肯定句，谓语动词需用延续性动词，表示主句的动作直到从句表示的时间点就结束。
eg: I will wait for you until/till you come back. 我会一直等，直到你回来。
eg: You may stay here until/till the rain stops. 你可以在这里一直待到雨停。
(3)用于句首时,常用until而不用tilleg: Until you told me, I had heard nothing of what happened.直到你告诉我以前，我一点都不知道出了什么事。
eg: Until the manager returns, nothing can be done. 经理不回来，什么也不能做。
5. before, after的用法before意为“.....之前”时,表示主句动作发生在从句动作之前。
after意为“.....之后”,表示主句动作发生在从句动作之后。
eg: Please turn off the lights before you leave the classroom. 请在离开教室前关上灯。
eg: He arrived after the game started. 比赛开始后他才到。
6. by the time 的用法by the time常用来指到某时间点为止，主句常用完成时态。
eg: By the time he was 12, he had travelled to more than 30 countries.到12岁为止，他已经去过30多个国家了。
eg: By the time I got outside, the bus had already left. 我到外面时，公交车已经开走了。
7. 名词短语引导时间状语从句的用法表示时间的名词短语有时也可以引导时间状语从句,常见的此类时间短语有the time the moment the minute the day the last time the second timeeach day every time next time any timeeg: The day he returned home, his father was already dead. 他到家的那天，他父亲已经去世了。
eg: He said he' d phone you the moment he got home. 他说他一到家就给你打电话。
eg: He was much better the last time I saw him. 上次我见到他时,他好多了。
eg: Every time I see him, he is working hard. 我每次见到他,他都在拼命地工作。
二、地点状语从句在句子中充当地点状语的从句称为地点状语从句。
引导地点状语从句的从属连词主要有where( ...地方), wherever(无论问处)等，表示地点方位。
eg: I found all the missing things where I left them. 我在丢东西的地方找到了所有丢了的东西。
eg: Where there is a will, there is a way. 有志者，事竟成。
eg: You are free to go wherever you like. 你可以随意到你喜欢的任何地方去。
eg: Wherever there is smoke, there is fire. 无火不生烟。