1.As可以引导定语从句.有时可译为“正如”.此时,常常是as从句在前,主句在后.
例如：As we can see,he is a Chinese.
2.As 还可引导
原因状语从句,“因为,由于”
例如：As he is so lazy,he never cooks by himself.
3.As还可引导
时间状语从句,“当,随着”
例如：As the weather is colder and colder,the leaves of the tree is less and less.
4.As还可引导
方式状语从句,“按照”
例如：You must do the work as I have told you.
5.As还可引导
让步状语从句.“尽管”.但是注意,as引导方式状语从句时从句必须倒装.而且这种倒装和一般的倒装不一样.as从句的倒装一般是把从句的
表语或作状语的副词提到as之前,（如果表语是一个带有
不定冠词a或an的单数名词,倒装后a或an必须省略).
例如：Though he is a little boy,he knows a lot.如果变成由AS引导,就必须变成：
Little boy as he is,he knows a lot.
Though he works hard,he never succeed.
可变为 Hard as he works,he never succeed.
as引导的方式状语从句和定语从句的区别
1.as作为连词可引导方式状语从句,意为“象……一样”,例如：
Remember,you must do everything as I do.记住,你们务必照我的样子去做每一件事.
But Americans still talk about “fall” just as people do in some parts of western England.但是美国人还是说 “fall”,就象
英格兰西部有些地区的人现在说 “fall” 一样.
2.as作为代词,通常以the same…as,such…as或as…as…的形式引导定语从句,as在定语从句中作主语、宾语或表语,例如：
作主语：As is known to all,coal is first discovered in China.众所周知,煤是最先在中国发现的.
作主语：As many people as were present knew the news.在场的人都知道这条消息.
作主语：Repeat this as often as is necessary.重复做这种动作的次数视需要而定.
作宾语：Such people as you mention are rare nowadays.你提到的那种人如今很少了.
作表语：He is not (= no longer) the same man as he used to be.他再也不是从前的他了.
3.as意为“当……”,引导时间状语从句；as强调主句动作与从句动作同时发生,通常译为“一边……一边……”,例如：
As the students watched him quietly,he mixed the three together.学生一边静静地看着他,他一边将三种东西混和起来.
which引导的定从和as引导的区别
which引导的定语从句和as引导的定语从句的区别：
1.as可以放在主句前后，也可插入主句之中；而which引导的非限制性从句只能位于主句之后。
As is known to all, fish can’t live without water.
Air, as we know, is gas.
2.在非限制性从句中，which后的
be动词不可省；as而后的be动词可以省略。
She told me she won the match, which was a lie.
The material is elastic, as (was) shown in the figure.
3. which在
非限制性定语从句做主语时可用各类动词做谓语；而as做主语时，谓语常用
系动词，如be, seem, become等，一般不用其他行为动词。
He saw the girl, which delighted him.
He didn’t say anything at the meeting , as/which seemed very strange.