状语从句（adverbial clause）
状语从句用来修饰主句中的动词，副词和形容词的从句，用作状语，起副词的作用。
状语从句一般由连词引导，也可以由词组引导。
状语从句位于句首或句中时，通常用逗号隔开； 位于句首时，可不需要。
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。
1. 时间状语从句。
1)常用连接词when, as, while, before, after, since(自从), till, until, as soon as（一….就。同义短语：
the moment, at the moment that，once），whenever(无论什么时候)例如：
it was raining hard（rain hard 下大雨） when got to school yesterday.
while he was doing his homework, the telephone rang.
as he walked along（沿着走） the lake, he sang happily.
he had learned a little chinese before he came to china.
after he finished middle school, he went to work in a factory.
2)常考点“主将从现”--在时间状语从句里，通常不用将来时态，用现在时态表示将来的动作或状态。例如：
i’ll ring you up as soon as i get to new york.
i will tell him everything when he comes back.
he won’t believe it until he sees it with his own eyes.
3)在带有till或until引导的时间状语从句的主从复合句里，如果主句用肯定式，其含义是“一直到……为止”，谓语动词只能用延续性动词。
the young man read till the light went out（熄灭）.
let’s wait until the rain stops.
如果主句用否定式，其含义是“直到……才……”在……以前不……”谓语动词可用瞬间动词。例如：
we won’t start until bob comes.
don’t get off（从下来） until the bus stops.
till是指直到某一特定事件发生的时候，而在那个时刻之后，该事情或状况仍将持续。
until是指直到某一特定事件发生的时候，而讲话的人在自己心里认为，在那个时刻之后，该事情或该状况将中止（不怎么可能持续）。
固定组合里from morning till night，till/until是不能替换的】
(4) since 自….以来到现在。
表示自过去的一个起点时间到目前（说话时间）为止的一段持续时间。
主句一般用现在完成时，从句用一般过去时。 (常用结构)
it is (has been) +一段时间 / 现在完成时 since 一般过去时/过去时间点/时间段+ago
5）when, while, as 的区别。
只用when的情况（后可接短暂性动词/延续性动词）：
“当…..时候”，
eg : 主从句事件发生有时间先后顺序时，（after,before）
when i got to the cinema, the film had already begun. (before) (经典题)
when he has finished his work, he takes a short rest. (after)
主从句动作同时发生。
when he rushed in, we were watching tv news
“就在那时”
eg were watching tv when the light went out.
“每当”（相当于each time） 过去或现在的习惯性动作。
eg: when he goes to town, he always visits his aunts.
when i lived in the countryside, i used to carry some water for her.
只用while的情况：
当….时候后接延续动词，强调主从句同时发生（或相对应）
while my wife was reading the news*****,i was watching tv.
“然而” 做并列连词，连接两个独立的句子，表示转折和对比。
i like playing football while you like playing basketball.
只用as的情况：
表示“随着” （主从句动作都变化）
as spring warms the earth, all flowers begin to bloom.
表示一个人的动作交替进行。
he looked behind from time to time as he went.
6）before 在…….之前。
如果before引导的从句谓语用的是过去式，则主句动词多用过去完成时。
my father had left for canada just before the letter arrived.
they had not been married four months before they were divorced.
2. 条件状语从句。
1)条件状语从句通常由if, unless (if ….not), as （so） long as (只要)引导。例如：
what shall we do if it snows tomorrow?
don’t le**e the building unless i tell you to.
you may use my bike as/so long as you return it before friday.
turn off the switch when anything goes wrong. (when 引导的从句也可以表示条件)
2)在条件状语从句里，谓语动词通常用现在时态表示将来的动作或状态。例如：
i’ll help you with your english if am free tomorrow.
he won’t be late unless he is ill.
3)“祈使句 + and (or)+ 陈述句” 在意思上相当于一个带有条件状语从句的复合句。例如：
hurry up, or you’ll be late. =if you don’t hurry up, you’ll be late.
study hard and you will pass the exam. =if you study hard, you will pass the exam.
3. 原因状语从句。
1)原因状语从句通常由because, since (now that), as, for引导。例如：
he didn’t come to school because he was ill.
as it is raining, we shall not （不得；不应该）go the zoo.
since you can’t answer the question, i’ll ask someone else.
2)because表示直接原因，而且这一原因通常是对方不知道的，语气最强。
because引导的原因状语从句多放在主句之后。回答由why提出的问题，只能用because。
because 可用于强调句。
eg: it was because he lost it that he found it more valuable than ever.
because和so不能同用在一个句子里。
as和since语气较弱，一般用来表示明显的原因(已知的事实)。由as和since引导的原因状语从居多放在句首。例如：
---why aren’t going there?
---because i don’t want to.
as he has no car, he can’t get there easily.
since we h**e no money, we can’t buy it.
because 引导的从句如果放在句末，常用for 代替。
he is absent today because/ for he is ill.
但如果不是说明直接原因，而是多种情况加以推测，只能用for
he must be ill for he is absent today.
for 是并列连词，表示推测的原因或对前一分句的补充说明理由。
eg: i t must h**e rained last night for the road is wet.
mary could not h**e seen me at the party, for i was not there.
4. 结果状语从句。
1)结果状语从句由so…that, such…that, so that, that引导。例如：
he is so poor that he can’t buy a bike for his son.
she is such a good teacher that everybody likes her.
my pencil fell under the desk, so that i couldn’t see it.
初中英语状语从句讲解 练习与答案
6 二氧化碳气体有什么特点？第三单元宇宙。3 米饭里面的主要成分是淀粉。米饭淀粉遇到碘酒，颜色变成蓝色，这种蓝色物质是一种不同于米饭和淀粉的新物质。冀教八年级 中考专题语法 状语从句。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...
初中英语定语从句讲解
match the two sentences reading a book.the book is about bill gates.i m reading a book that which is about bill gates.is a teacher.the teacher teaches...
初中英语定语从句讲解
match the two sentences reading a book.the book is about bill gates.i m reading a book is about bill gates.is a teacher.the teacher teaches us chinese...