状语从句在句中作状语，修饰主句中的动词，形容词，副词等。状语从句放在主句之前，常用逗号分开；放在主句之后，一般不用逗号。状语从句按其意义和作用可分为时间、条件、原因、让步、目的、结果、方式、比较、地点等九种。
状语从句定义及分类
状语从句就是用不同的连接词将几个分句连接起来，以表达分句之间特定的逻辑关系。
（一）时间状语从句
1、时间状语从句常用连词有when, as, while, before, after, since, till, until, as soon as, when, scarcely…when, no sooner ... than, the moment, the instant等。
2、时间 /条件状语从句一般不用将来时，因此，主句若为将来时，时间状语从句要用一般现在时。
eg. I'll go on with the work when I come back tomorrow.地狱少女台词
3、连词when, while和as都表示“当…的时候”，
when 后接时间点或时间段，表“当…时候”；还可表示“这时，忽然”（用在句型中）及“既然”
while 后只可接时间段，表“当…时候”；还可表示 “而，然而”
as 引导持续性动作，强调主句和从句的动作同时发生，译为“一边…一边”
迟疑不决eg. While/when I was reading, he came in.
When he came in, we were having a meeting
As he walked along the street, he sang happily.
4、till或until表示“一直到…时”，主句和从句都用肯定式，主句用延续性动词；表示“直到…才…”时，主句用否定式，用终止性动词，从句用肯定式。till不能置于句首。
e.g He worked till/ until it was dark.
He did not get up till/ until his mother came in.
注意till / until在表达方式和意义上的特殊性：until是till的强调形式，但是它们表达的意义是相同的，都表示“直到某时”。不过，当主句是否定句时，它引出的意思是“直到（某时）（某动作）才（发生）” ，这时候常会出现“not until …”的结构，如果将 “not until …”的结构放在句首，那么主句要写成倒装句。例如：
He didn’t go to sleep until 12 last night .
他昨晚直到十二点钟才睡觉。
They didn’t realize their fault till we pointed it out to them .
直到我们向他们指出了他们的错误，他们才意识到。
Not until we pointed out their fault to them did they realize it .
直到我们向他们指出了他们的错误，他们才意识到。
但是，当主句是肯定句时，它引出的意思是“直到（某时某动作停止了）” 。例如：
The students made much noi till the teacher came into the classroom .河南郭亮村风景区
小学绘画
直到老师走进教室学生们才停止了大声喧哗。
另外，until 可以放在句首而till则不行。
5、as soon as, the instant和the moment/ the minute/ the cond引导的从句表示“一…就…”；han, when, when引导的从句表示“刚…就…”，主句中的动词一般用过去完成时，从句用一般过去时，而且当此短语置于句首时，主句应半倒装。
e.g. I recognized her the instant I saw her.
Hardly had I entered the room when I heard a noi.
5、before & since
①若表达“还未…就…”“不到…就…”“…才…” “趁，还没来得及”时，用before, 从句中谓语不
用否定式。
eg. We had sailed four days and four nights before we saw land.
We hadn’t run a mile before he felt tired.
Plea write it down before you forget it.
Before I could get in a word, he had measured me.
②It + be + 时间段 + before … “多久之后才…”
It + be +not + 时间段 + before … “没多久就…”
e.g. It will be half a year before I come back.
It wasn’t long before we met again.
③since从句的谓语动词一般是终止性动词，主句的谓语动词是延续性的或表示反复发生过的动作。从句的时态若是 一般过去时，主句的时态是现在完成时或现在完成进行时。
e.g. I have written home four times since I came here.
④It + be+ 时间段 + since +一般过去时 延续性动词（反义
过去完成时 终止性动词（直译）
eg. It is 3 years since she was my wife.
It is 3 years since she became my wife.
Her mother said it was 12 years since her father had died.
He said it was 2 weeks since he had smoked.
（二）原因状语从句
常用becau, since, as, for, now that等引导。
becau 强调从句, 表直接的因果关系侧重回答“为什么”
as 主从句并重，较口语化，用得较普遍
since 侧重主句, 从句所表示的只是显然的或已知的理由,“既然”
now that “既然”,和since的意义和用法相同, that可省, 用来表示一种新的情况, 再来加以推论。
for 语气最弱，不能置于句首，表补充说明的或推测的理由( 并列句）
Now (that) you are free today, you may have a rest at home.
（三）地点状语从句
地点状语从句常用where, wherever等连词引导；注意不要和where引导的定语从句相混淆。
eg. Make a mark where you have questions
9月放假Make a mark at the place where you have questions.
四字吉祥语
（四）条件状语从句
条件状语从句用if, , as/so long as (只要), in ca(万一), on condition that(条件是), suppo (that) (假设，用于问句), provided (that)等词引导。如果主句是将来时，条件状语从句用一般时表示。
eg. As long as I live, I shall work hard.
I shall not go to school unless I finish my homework.
In ca there is a fire, what will you do first?
Suppo (that) they refu us, who el can we turn to for help?
（五）让步状语从句
让步状语从句由although/though, as, even if, however, whatever, no matter 等词引导。
eg. Although he is clever, he doesn't study well.
No matter who asks for advice,she is always ready to help.
十四只老鼠注意：由as引导的让步状语从句，须将作表语的形容词或名词（不用冠词）放在句首。
eg. Clever as he is, he doesn't study well.
Child as he is , he knows a lot.
as引导的让步状语从句必须用倒装形式(as = though )单数名词前不要a/ an；形容词或副词前不要very。
例句：
1. Although she is busy, she studies English very hard
Busy as she is, she studies English very hard.
2. Although he is a doctor, he knows medicine no better that I. Doctor as he is, he knows medicine no better that I.
与项羽有关的成语
3．Although I admire him as a writer very much, I do not like him as a man.
