as作關系代詞
不僅可以代替一個名詞，而且可以代替整個句子或一件事，通常譯作“正如這一點”，“如……一樣”。
As is known to everybody, the moon travels around the earth once every month.
如同大家所知道的一樣，月亮每月圍繞地球旋轉一次。
As has been said before, grammar is not a set of dead rules.
如同以前說過的一樣，語法并不是一套死規則。
Such a clever girl as she can learn anything quickly.
像她這樣聰明的女孩子學任何東西都很快。
It was absolutely bad manners to get into people's room without knocking, as quite a few young people are doing every day.
不敲門就進入別人的房間絕對是不文明的行為，現在很多年輕人每天都這么干。
as構成固定詞組
1. as可以構成介詞詞組
as against 與……相比；as compared with 與……對比；as for/to 至于，關于；as from/of 自……起；as a result of 由于……的結果；as regards 至于
As regards salary, I leave it to you to decide after experience of my capacity.
關于薪水，請你們考驗本人能力后再作定奪。
The output amounts to ten thousand dollars as against eight thousand last year.
和去年八千美元的產量相比，今年的產量達到了一萬美元。
There is no doubt as to who will be elected.
至于誰會當選，這是毫無疑問的事。
The only exception was the year of 1991, when there was a slight decline as compared with the previous year.
唯一例外的是1991這一年，與前一年相比略微有所降低。
As a result of your carelessness, the whole project should be put off at least one month.
由于你的粗心，整個計劃將要被推遲至少一個月。
2. as可以構成副詞詞組：
as above 如上；as follows 如下；as a matter of fact 事實上；as a whole 就整體來說；as good as 和……幾乎一樣，實際等于；such / so … as to 這樣的……以至于……；as yet 尚，至今還（用于否定句）；as well 也
As a matter of fact, he didn't have any interest in the project.
事實上，他對這個項目一點興趣都沒有。
I am not so foolish as to make such a promise.
我還沒有愚蠢到會許下這樣的承諾的地步。
His mother was so ill that she was as good as dead.
他的母親病得很厲害，就跟死了一樣。
3. as構成詞組作關系代詞：
as...go 就……一般情況來說；as it is / was 事實上，按現狀；as it were 仿佛是
He is quite good, as boys go.
就一般男孩子而言，他已經很好了。
I thought conditions would get better, but as it was, they were getting worse.
我以為情況會好轉，但事實上，卻是越來越糟糕。
He was, as it were, intoxicated by the soft air and sunshine of spring.
他仿佛像往常一樣陶醉于春天溫馨和煦的陽光和空氣里。
4. as可以構成連詞詞組：
according as 根據，按照……而；in as (so) far as 根據……程度
You may go or stay, according as you decide.
你可以自己決定是去還是留。
In as (so) far as we have known about the matter, we can make a decision after the meeting.
就我們對這件事情的了解程度，我們可以在會后作出一個決定。