（一）状语从句概述 定义 位置 状语从句用作状语，是起副词作用的句子。 状语从句可以放在主句之前，也可以放在主句之后，时间、条件、原因和让步状语从句放在句首时需要用逗号和主句隔开。 分类 根据其作用可以分为时间、地点、原因、条件、目的、让步、方式和比较等状语从句。 作用 它可以修饰谓语、非谓语动词、定语、状语和整个句子。
（二）状语从句详解 1. 时间状语从句 引导词 when 用法 意为“当…的时候”。When引导从句的谓语动词可以是延续性动词，也可以是瞬间动词。并且when有时表示“就在那时” 示例 A liar is not believed when he speaks the truth.说谎者讲真话时也没有人相信。 When he arrives, I’ll call you. When you laugh and smile, your body relaxes. while 意为“在…的时候，在…的同时”。While引导从句的谓语动词必须是延续性的，发生时间较长，并强调主句和从句的动作同时发生（或者相对应）。While有时还可以表示对比。 While I was standing at the window, I saw several boys running along the street. While John was watching TV, his wife was cooking. as 意为“一边…一边…”。As引导的动作是延续性的，发生时间较短，一般用于主句和从句动作同时发生；as也可以强调一前一后。 The writer was angry as he was travelling on a train to London because someone had invaded his “space”. He smiled as he stood up. after 意为“在…之后”。表示主句动作发生在从句动作之后。主句与从句的动作时间关系与before引导的从句相反。 With many hungry visitors waiting, don’t stay too long at your table after you have finished. If an early exit is necessary, you can leave after a scene is over. before 意为“在…之前”。引导的从句不用否定形式的谓语，并且当before引导的从句位于主句之后，有时译成“就，才”。当主句用将来时，从句总是用现在时；如果before引导的从句谓语用的是过去时，则主句动词多用过去完成时，这样以便体现动作的先后。 You can’t watch TV before you finish your homework. Before it ended, the theatre was almost empty. My father had left for Canada just before the letter arrived. till 意为“直到”。一般情况下可以和until互换。如果主句中的谓语动词是瞬时动词时，必须用否定形式；如果主句中的谓语动词是She didn’t even know that it was an earthquake till she saw a shaking ( moving from side to side) light. The fireman worked very hard 延续性动词时，用肯定和否定形式都可以，但表达的意思不同。 until 意为“直到”。在强调句型中多用until。如果主句中的谓语动词是瞬时动词时，必须用否定形式；如果主句中的谓语动词是延续性动词时，用肯定和否定形式都可以，但表达的意思不同。 since 意为“自从，从…以来”。引导从句的谓语动词可以是延续性的动词，也可以是瞬时动词。一般情况下，从句谓语动词用一般过去时，而主句的谓语动词用现在完成时。但在It is +时间+since从句的句型中，主句多用一般现在时。 as soon as 意为“一…就…”。引导时间状语从句时，如果主句用了将来时，从句一般使用现在时。
2.地点状语从句 引导词 where 用法 意为“哪里”。“where引导的地点状语从句，（there+）till the fire was out. I’m waiting for my sister. I won’t go to see my uncle until she comes. Wait until I finish what I am doing. I have been studying hard since I entered the high school. It is four years since my sister lived in Beijing. It is five years months since our boss was not in Beijing. Tom will call me as soon as he gets home. I will call you as soon as I arrive. 示例 Where there is a will, there is a way. 主句”“哪里…哪里就…”。主句在从句后面时，there可用可不用；主句在从句的前面时，一般都不用there. They were good persons. Where they went, there they were warmly welcomed. You should have put the book where you found it. wherever 意为“无论何地”。anywhere/wherever引导地点状语从句+主句。anywhere本身是个副词，但是常可以引导从句，相当于连词，意思相当于wherever, anywhere引导的从句可位于主句之前，也可以位于主句之后。而wherever本身就是个连词，表示“在何处，无论何处”。 Wherever the sea is, you will find seaman. I’ll go anywhere you go.
3.条件状语从句 引导词 if 用法 连词，意为“假如，如果”。当主句是将来时的时候，从句要用一般现在时。 示例 Don’t talk loudly at the meeting. If you do, you will have to leave. We’ll go for a picnic if it doesn’t rain this weekend. unless 连词，意为“除非（=if not）。当主句是将来时的时候，从句要用一般现在时。 Don’t discuss the problems with your partner unless you are asked to do so. I won’t go there unless you come with me.
4.原因状语从句 引导词 as 用法 意为“因为”。引导原因状语从句时表示附带。说明“双方已知的原因”，语气比since弱，较为正式，位置较为灵活（常放于主句之前）。 since 意为“因为”。引导的原因状语从句一般放于主句之前表示已知的、显然的理由（通常被翻译成“既然”），较为正式，语气比because弱。 示例 As the weather is cold, I stay at home. As it is raining, you’d better take a taxi. As you are tired, you’d better rest. Since the earth looks like a ball, the sun can shine on only half of it at a time. Since the race is in April, I had to run throughout the winter, and in Boston, winters are cold. Since everybody is here. Let's begin our meeting. because 意为“因为”。引导的原因状语从句一般放于主句之后，表述直接原因，语气较强，最适合why引导的疑问句。Because引导的原因状语从句有时可以与because of短语互换。 The woman prefers winter because she can skate. I’d like to collect stamps because they are interesting. I’m very tired these days because of studying physics. He can’t come because he is ill. = He can’t come because of his illness. for 意为“因为”。引导的原因状语从句并不说明主句行为发生的直接原因，只提He must be ill, for he is absent today.
初中状语从句讲解及习题附答案
