本博文源于《语法知识清单》，今天讲解三大从句之一状语从句，状语从句的种类共九种，而九种之下其实内容不多，合在一起就显得有点繁杂，阅读博文时从目录出发，把目录驾轻就熟，方能心中有丘壑。
用作状语的从句叫状语从句，又由于其功能与副词非常相近，故又称作副词性从句。一般可分为时间、地点、原因、结果、方式、条件、目的、让步、比较类型。
[英语语法]词法之连词
此篇博文在引导状语从句的连词中有详细叙述了。
时间状语从句
when,while和as的用法
- When I lived there,I used to go to the park on Sundays.
- She hurried home,looking behind as she went.
till,until的用法
延续性动词(肯定式)+until/till 表示 + “动作延续到…为止”
- You may stay here until/till the rain stops.
瞬间动词/非延续性动词(否定式)+until/till表示“直到…才发生"
- He won’t go to bed until she retuns.
强调句型：It is not until…that+…
- It was not until you told me that I had any idea of it.
since 的用法
since引导的时间状语从句表示"自从…以来".从句常用一般过去时，主句常用现在完成时或现在进行时，加强语气时可用ever since.常用句型为"It is/has been+时间段+since从句"
- It is two years since we arrived here.
since引导的时间状语从句的谓语动词一般用非延续性动词，主句动作时间的起点应为从句动作发生时；从句若用延续性动词，则主句动作时间的起点应为从句动作结束时
- It is more than ten months since I worked in the city.
by the time,each time,next time,the last time,any time,the first time,the moment等可直接引导时间状语从句
- The moment I get the ticket,I’ll send it directly to you.
表示“一…就”的引导词有:as soon as,the moment,the instant等
- The boy burst into tears immediately the saw the mother.
地点状语从句
它的引导词有：where,anywhere,everywhere,wherever等
地点状语从句表示地点、方位通常可置于句首，句中，句尾。
- Where there is a willing there is a way.
- You are free to go anywhere you like.
原因状语从句
when(既然)相当于considering that
- It was foolish of you to take a taxi when you could walk there in five minutes.
in that表示"由于某种原因"
- The experiment is worth trusting in that it is based on scientific facts.
目的状语从句
常用so that,in order that,for fear that,in case 等引导
so that 与in order that
都可翻译为"以便…""为了…"它们引导的状语从句中常用情态动词。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，so that短语中有时可省略that.
- In order that we could save time we used the computer.
for fear that 与in case
引导目的状语从句时，for fear that表示"害怕/担心发生某事"，in case 表示”以防发生某种情况“，从句中有时可用虚拟语气(should+动原)
- Take your raincoat in case it should rain/it rains/
结果状语从句
结果状语从句可以与too…to…(太…而不能…),enough…to…(达到某种程度可以…),so …as to (那么…以至于…)等结构进行转换
He didn’t get up early enough to catch the bus.
=He got up too late to catch the bus.
=He got up so late as to miss the bus.
条件状语从句
常用引导词为if,unless(=if…not如果不;除非),so/as long as(只要),in case(万一)等.在条件状语从句中，用一般现在时代替一般将来时，一般过去时代替过去将来时。
- You’ll fail the exam unless you study hard (=if you don’t study hard).
让步状语从句
though/although的用法
- though/although 引导让步状语从句，主句可用yet或still，更加强调对比性，但不可用but。
- though引导的从句可用倒装
例子：
Although/Though it was raining hard.(yet) they went on playing football.
even though/even if的用法
意为“即使，尽管”，引导的从句可用陈述语气，也可用虚拟语气。
例子：
Even if I were busy,I would go.
as的用法
as引导让步状语从句时常采用倒装形式，可倒装名词、形容词、副词或动词(though引导的从句可以像as引导的从句一样用倒装语序，although引导的让步只能用正常语序)
例子：
Try as/though you may,you will never succeed.
（=Though/Although you may try,…）
while的用法
while也可作从属连词引导让步状语从句，相当于although。while多用于句首。
- While I admit that there are problems,I don’t agree that they cannot be solved.
wh-ever类引导词的用法
在英语中wh-ever类的词可引导让步状语从句，相当于“no matter+相应的 wh-词”
whether or not/whether…or(not)引导的让步状语从句
- Whether or not you help me,I’ll do it.
比较状语从句
原级比较的用法
原级比较的肯定式常用as…as…结构
- There are as many people in our town as(there are ) in your town.
原级比较的否定式常用not as/so…as…结构
- His handwriting is not as/so good as yours(is).
比较级的比较
比较级比较常用结构为…than…
- He comes to the club less often than he used to.
the + 比较级…,the + 比较级…
- The sooner you are back,the better it will be.
方式状语从句
在句子中作方式状语的从句称为方式状语从句。方式状语从句一般位于主句之后。常用的引导词为as,as if,as though等
as if/as though的用法
as if或as though引导的从句一般用虚拟语气，但如果从句中所陈述的情况很可能实现，也可用陈述语气。常与look/seem/taste/smell/sound等词连用
- The injured man acted as if nothing had happened to him.
状语从句的省略
在状语从句中，为了使语言更加简洁、生动、经常运用省略形式。如果从句主语和主句主语一致，就可以经过一定的变形把状语从句中的主语和谓语的一部分或全部省略。
在时间状语中
- When (she was ) very young,she began to learn to play erhu.
在条件状语中
条件状语从句的省略形式为if necessary,if possible,if true等。另外unless,as long as 等词或短语后也可运用省略形式.
- He will come if (he is) asked.
