状语从句是英语语法中的常用句型语法，那么大家是否清楚什么是状语从句呢?下面就是小编给大家带来的初中英语状语从句详细解析，希望能帮助到大家!
状语：是用来修饰动词、形容词、副词或全句用的。
eg：He works hard! (他努力工作)中的hard。
状语的位置：
修饰形容词或副词的状语放在被修饰语之前。
eg：The Summer Palace is very beautiful.颐和园非常美丽。
(very 为状语，修饰形容词 beautiful，放在 beautiful 之前)。
修饰动词的状语有的放在动词前，有的放在动词之后。
如果动词有宾语，状语一般须放在宾语之后。
eg： I He often came here to see me.他经常到这里来看我。(often 为状语，修饰动词came，放在前面)。
I know him well.我十分了解他。(well为状语，修饰动词 know，放在 know 之后)。
状语从句：用一个句子(从句)来作另一个句子(主句)的状语，用作状语的句子就叫作状语从句。作什么样的状语就叫什么类型的状语从句。例如：条件状语从句就是用一个句子来作条件状语。
(1)时间状语从句
凡是从句都必须有引导词，引导时间状语从句的词有when，before，after，until，as soon as，while 等，具体用法如下：
1. when 意为“当……时”，引导时间状语从句，表示主句的动作和从句的动作同时或先后发生。
eg: I feel very happy when you come to see me.
When you are crossing the street，you must be careful.
when引导的时间状语从句，when的从句可以用延续性动词，也可以用瞬间动词。
eg：He was working at the table when I went in. 。
Someone knocked at the door when I was sleeping.
I will visit my good friend when I have time.
注：when也可以作并列连词，表示一个动词正在进行的时候，突然间发生了另外一件事。
eg: I was fishing by the river，when someone called for help.
We were working in the chemistry lab，when the lights went out.
2. before 意为“在……之前”，引导时间状语从句时，表示主句的动作发生在从句的动作之前。 eg: We cleaned the classroom before we left school yesterday.
He had been a cook before he went to college .
after 意为“在……之后”，引导时间状语从句时，表示主句的动作发生在从句的动作之后。
eg: After you use plastic bags，you mustn't throw them about.
He called me after he had finished his work.
注：若主句和从句两个动作发生的先后顺序十分接近，那么也可以不用完成时态，如上面的 第二句可改成：He called me after he finished his work.
3. since引导的时间状语从句，译为“自从……”，主句常用现在完成时，从句常用一般过去时。
eg: I have taught English, since I came to Shenzhen.
注：常用句型：It is +时间段+since从句 译为：自从……有多长时间了。
eg. It is six years since she graduated from the university.
4. until 意为“直到……时”，引导时间状语从句时，表示主句的动作发生在从句的动作之前。
当主句的谓语动词是持续性动词时，主句常用肯定形式;当主句的谓语动词是非持续性动词时，从句常用否定形式，not…until… 意为“直到……才……”，这时的until可以用before 来替换。
eg：I'll stay here until you come back.
我会呆在这里，直到你回来。 (stay表示的 动作可以持续)
He didn't go to bed until he finished his homework.
他直到做完作业才睡觉。(go to bed 表示的动作不能持续)
5. as soon as 意为“一……就……”，表示从句的动作一发生，主句的动作马上就发生。
eg：I'll tell him about it as soon as he comes back.
6. while引导的时间状语从句，常译为“与……同时，在……期间”，while的从句中常用延续性动词或表示状态的词。
eg. They rushed in while we were discussing problems.
Father was cleaning the car while I was playing computer games.
注：while也可以作并列连词，表转折的关系，相当于but，译为“然而”。
eg. I like listening to music，while my brother likes doing sports.
7. till和until引导的时间状语从句，译为“直到……为止”，not … till / until引导的时间状语从句，译为“直到……才”。前者强调主句动作的结束，用延续性动词，后者强调主句动作的开始，用瞬间动词。
eg. I will wait for my friend until / till he comes. 我要一直等到我朋友来。
We won't start our discussion until / till he comes.
我们要等到他来了，再开始我们的讨论。
(2)条件状语从句
1.条件状语从句通常由if, unless引导。
eg：What shall we do if it snows tomorrow?
Don’t leave the building unless I tell you to.
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。(主将从现)
eg：I’ll help you with your English if I 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。
eg：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, as引导。
eg：He didn’t come to school because he was ill.
As it is raining, we shall not go the zoo.
Since you can’t answer the question, I’ll ask someone else.
2. because表示直接原因，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。As和since语气较弱，一般用来表示明显的原因。由as和since引导的原因状语从居多放在句首。
eg：------Why aren’t going there? ------Because I don’t want to.
As he has no car, he can’t get there easily.
3. because和so不能同用在一个句子里。
For 语气最弱，它所引导的分句必须放主句后面，引补充说明作用。
eg：Put on more clothes, for it's cold outside.
注：because, since, as, for 的区别
语气 位置 意义
because 最强 前或后 “原因”;表客观因果关系;回答“”
as 较强 前 “由于”;把众人所知的事实当作理由
since 较弱 前 “既然”;就对方陈述的事实作为理由
for 最弱 后 “理由”;对某一事实进行推断的理由
(4)地点状语从句
常用where(哪里)和wherever(无论哪里)
eg. Where there is a will，there is a way. 有志者，事竟成。
We will go wherever the motherland need us most. 我们要到祖国最需要的地方去。