状语从句
定义：
在句中作状语的从句是状语从句，修饰主句中的动词、形容词或副词等。状语从句由从属连词引导，从属连词在句中不充当句子成分，只起连接作用，状语从句放在句首时，要用逗号，放在句尾时不用。
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。
尽管种类较多，但由于状语从句与汉语结构和用法相似，所以理解和掌握它并不难。状语从句关键是要掌握引导不同状语从句常用连接词
和特殊的连接词即考点。现分别列举如下:
一、 时间状语从句
1.when, while和as的用法
(1)when既可引导一个持续动作，也可引导一个短暂性动作. when强调主从句动作的发生有先后。如：
①When he got there, the classroom had been cleaned.
他到的时候，教室已打扫过了。(主句动作发生在从句动作之前)
②He went to play football when he finished his homework.
做完作业后他就去踢足球了。(主句的动作发生在从句动作之后)
when可作并列连词用，相当于just then，at the time，前一分句多用进行时、be about to或be on the point of doing，表示“正在做..，就在这时发生了另外一件事”或“届时”。如：
①I was reading when he suddenly came in.
②I was about to leave when the telephone rang.
(2)while强调主句动作发生在从句动作所发生的时间段内，从句的动作必须是延续性动词。如：
①Strike iron while it’s still hot.
②Will you plea take care of my hou while I was away?
annex在这一情况下，从句的动作一定是延续性动词，如果是非延续动词，要用when。如：
①Will you plea take care of my hou when I went away?
②当我进来的时侯，他在和别人说话。
While I came in, he was talking with others.
When I came in, he was talking with others.
(3)as引导一个持续性动作，强调主从句的动作同时发生，有“一边..一边..”的意思，也可说明两种正在发展或变化的情况，有“随着..”的意思。如：
braid①He sang as he walked.他边走边唱。
②As he gets older, he gets more open.
随着年龄的增长，他越发开朗起来。
2.as soon as, the moment, the minute, the cond, the instant, han, ，immediately, directly, instantly的用法。
这些从属连词引导的从句都表示从句动作一发生，主句的动作随即就发生，常译为“一……就……”，
The moment she arrives，we can start.
No sooner had we arrived at the station than the train left.
The boy burst into tears immediately he saw his mother.
3.till, until和until的用法
(1)在肯定句中，主句谓语动词必须是延续性动词，意为“某动作一直延续到某点才停止”。
You may stay here till/until the rain stops.
你得在这里呆到雨停。
(2)在否定句中，主句谓语动词必须是非延续性动词，从句为肯定式，意为“某动作直到某时间才开始”。
He won't go to bed till (until) she returns.
直到她回来他才睡。
(until句型中的强调和倒装说法。
It was not until you told me that I had any idea of it. (强调句型)
Not until you told me did I have any idea of it. (not until 置于句首，主句要倒装)
Not until he came back did he find his hou had been broken into.
4.before和since的用法
(1)连词before表示“还未……就……”，“不到……就……”，“……才……”，“趁还没来得及……”。
Before they reached the station, the train had gone.
七大洲英文
We hadn't run a mile before he felt tired.
Plea write it down before you forget it.
(2)before的句型：古铜色英文It will be＋时间段＋ before从句，表示“多久之后才……”。
It will be half a year before I come back.
batter
It won't be long before we meet again.
(3)since的句型： It is/has been＋时间段＋ since从句。若从句谓语为非延续性动词，表示“自从……有多久”；若从句的谓语为延续性动词，表示“自从结束/完成……起有多久”。
It is three years since the war broke out. 相信的英文
It is three years since he lived here.
二． 地点状语从句
1.地点状语从句可用where, wherever, anywhere, everywhere等引导。地点状语从句可用于主句之前或之后。
You are free to go wherever you like.
Where there is a will, there is a way.有志者，事竟成。
Wherever there is smoke, there is a fire.
无火不生烟(既无风不起浪)。
2.注意区分引导的定语从句与状语从句。
where引导的地点状语从句直接修饰动词，而在定语从句中where作为关系副词要跟在表
示地点先行词后面。
You'd better make a mark where you have any questions.(状语从句)
You'd better make a mark at the place where you have any questions.(定语从句)脸骨
客套话三． 原因状语从句
1.引导原因状语从句的从属连词有： becau, as, since, now that, eing that, considering that等，每个连词的含义不尽相同。
take it to the head
(1)becau用来回答why的提问，语气最强，一般放在主句之后；
(2)since表示既然或已知的理由，稍加分析即可表明原因，多放在句首；
(3)as 多用于口语，语气比becau，since弱，表示的理由是明显的或被认为是已知的，是对主句的附带说明，重点在主句，可放在句首或句尾，放在句尾时，as可省略。
I can’t go，(as) I am busy.
(4)considering that, eing that, now that和since的意义相似，都有“鉴于某个事实”的意思，that可以省去。
As it is raining, we shall not go to the park.
Now that/Since everybody is here, let's begin our meeting.既然大家都到了，我们就开始我们会议。sinna
My friends dislike me becau I’m handsome and successful.
Now that everybody has come, let’s begin our conference.
四． 目的状语从句
引导目的状语从句的从属连词有：so that, in order that, for fear that，in ca, lest等。
1.in order that与so that
两个连词都意为“以便……，为了……”，引导的状语从句中需用情态动词；in order that比
so that正式，引导的状语从句可置于主句之前或之后，而so that引导的从句只能置于主句之后。
I'll speak slowly so that you can understand me.
In order that we might e the sunri, we started for the peak early.
The boss asked the cretary to hurry up with the letters so that he could sign them.
2.for fear that, in ca与lest这些从属连词本身带有否定意义，意为“以免，以防”，相当于.或in .
The boy hid himlf behind the tree in ca/for fear that his father should e him.
