Grammar: The Performance of "as"
语法：as的使用

"as"是个非常活跃和多面的词，出现频率极高，充分认识它有助于我们更好地掌握英语。

1. as作连词

1）表示时间
As winter approached, the weather became colder.
As they were playing basketball, it began to rain.

2）表示原因（强调客观原因）
As you are the employee of the company, you must abide by the rules.
As the professor was not present, the meeting was canceled.

3）表示让步（语气比although / though强，部分到装）
Much as I like my wife, I am really annoyed with her sometimes.
Cold as it was, the farmers continued their work in the field.

4）表示方式
Leave as it is.
Things happened just as they were predicted.

5）表示比较

a. 在as…as / not so…as结构中，第一个as前可以用表示倍数、程度的词。如：
She is not so clever as her sister (is).
This stack of newspapers is twice as high as that of leaflets.

b. 在as…as结构中，如果有带an /a的名词，注意这个结构的语序。
Jackie is as good an actor as his father.
He is as successful a writer as Hemingway.

C. 在as…as结构中，注意第二个as后人称代词的形式。
He likes cartoon films as much as every child (likes them).
Lily hates her husband as much as his friends. (Lily hates her husband and hates his friends, too.)
The hostess welcomed him as much as me.

d. as…as结构的灵活表现。
The old man found reading as interesting as writing.
It is as easy as eating a piece of cake.
You look as pretty as ever.
All the rooms in this hotel are as clean as required.

2．as作关系代词:

不仅可以指代一个名词，还可以代替整个句子或一件事，这时其功能类似引导非限制性从句的which，which从句只能放在其修饰的句子后，而as带起的从句既可放在所修饰的句子后面也可放在其前面。 As is always said, English grammar is not just a set of dead rules.
The Sun is the center of the solar system, as is known to everyone.
They accepted as many students as had been recommended.

3．as作介词 (像…一样)

1）as 和 like的区别
They were united as one man.
He behaves as a businessman. (He is a businessman)
He behaves like a businessman. (He is not a businessman)

2）as引导的介词短语作宾语补足语
I don't regard him as dangerous as he looks.
Every student considers a dictionary as very useful.
Tom regards John as his best friend.

3）as引导的介词短语作主语补足语
The report was considered as boring.
He stood there as a sign.
His life as an executive officer came to a sudden end.

4．as作副词: 表示程度、数量、质量上"一样地…"。如：

My brother earns a lot working in the bank, but I can't earn as much.
The little boy gets the highest score on the test, but not everyone can be as intelligent.