如何区分as引导的方式状语从句和定语从句

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。

方法是：
1.方式状语从句通常由as, (just) as…so…, as if, as though引导。
（1）as引导行为方式状语从句时,意为“如同……”､“按照……的方式(样子,办法)”｡这种从句常位于主句之后｡
（2）(just) as…so…结构中位于句首，这时as从句带有比喻的含义，意思是"正如…"，"就像"，多用于正式文体。
（3） as if/though引导的方式状语从句比较容易区分。　

2.as引导限制性定语从句时,构成“the same ... as ...”, “such ... as ...”, “as many (much, few, little) ... as ...”等结构｡ as可替代先行词,在从句中作主语､表语､宾语或状语｡

3. as引导的非限制性定语从句,可以修饰整个主句和主句中的一部分｡从句可位于主句之前､句中或主句之后,通常用逗号将其与主句隔开｡这时as可译为“正如”､“正像”｡
常见的这种定语从句还有: as has been said before(如前所述); as is mentioned above(如上面提到的); as may be imagined(正如可想象的那样); as is well known to us all(众所周知); as (sb) all know(众所周知); as often happens(正如经常发生的那样); as has already been pointed out(正如已经指出的那样); as we all can see(正像我们都能看到的那样)等｡