1. 方式状语从句: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｡例如:
You must try to hold the tool as I do. 你必须像我这样拿工具｡
Leave the things as they are. 别动这些东西｡
We must do as the Party tells us (to do). 我们必须按照党的指示办事｡
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.
例如： Always do to the others as you would be done by. 你希望人家怎样待你，你就要怎样待人。
As water is to fish, so air is to man. 我们离不开空气，犹如鱼儿离不开水。
Just as we sweep our rooms, so we should sweep backward ideas from our minds. 正如打扫房屋一样，我们也要扫除我们头脑中落后的东西。
2) as if/though引导的方式状语从句比较容易区分,这里不做解释.
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｡
例如: He isn’t the same person as he used to be. 他不再是过去那个样子了｡
I have never heard such a story as he is telling. 我从来没有听见过像他正在讲述的这种故事｡
Here is a bottle of pure water. You may use as much of it as you need. 这里有一瓶纯净水,你需要多少就用多少｡
This is the same watch as I have lost. 这块表和我丢失的那块表一样｡
In those days, many youths lived in the same way as the villagers did in the mountains. 那些日子里很多青年人跟山区的老百姓一样生活｡
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”｡例如:
As is reported in the newspaper, talks between the two countries are making progress. 正如报纸上报道的那样,两国之间的会谈正取得进展｡
He is an Englishman, as I know from his accent. 从他的口音,我知道他是英国人｡
As was usual with him, he went out for a walk after dinner. 像往常那样,他吃完饭后就出去散步了｡
As is often the case, we have overfulfilled the production plan this year. 像往常一样,我们今年又超额完成了生产计划｡
This machine, as might be expected, has stopped operating. 正如人们所料,这台机器已停止转动了｡
He came very early this morning, as (was) usual. 像往常一样,他今天早上来得很早｡
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｡
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