As可以用做的词性：代词，介词，副词，连词
一、作代词（关系代词）
As作关系代词引导定语从句可以单独使用，也经常与一些词连用
1. 用在the same……as 结构中
Eg：
He bought the same refrigerator set as you had.（做宾语）
The same accident as happened to you, had happened to me.（做主语）
He is not the same playboy as we knew.
This is the same book as I lost.（这是我丢失的那本书）
对比：This is the same watch that/which I lost.(是同一只手表)；所以same和such后面有时也可以用who which that引导从句，只是意义上有时会有差别。
2.用在such as 结构中
I don’t like such books as he recommends.
He is not such an idiot as he looks.
Such a dog as I keep is called bulldog.
Children love such people as love them.(主语)
Such a student as works hard will succeed.(主语)
注意such as后面有时跟一些名词作为例子，而不是从句。可以such as+例子，也可以such+名字+as+例子
He has such books as Iliad and Hamlet.
He has many books, such as Iliad and Hamlet.
Many books are available in Manhattan English, such as Iliad and Hamlet.
Some cities have millions of people , such as Beijing and New York.
3.so+ adj+a/an+N.+as结构（注意对比such a /an+adj）
He is not so weird a person as he was.
He can write so interesting a story as moves us to tears.
He did it in so peculiar a manner as surprised me.
4. as单独使用引导一个定语从句，先行词可以是一个名词、句子、短语
He shouted at the little boy, as is often the case.(非限制性定语从句，as代指前面整个句子)
As is well known(to everybody), the moon travels round the earth.
To shut eyes to facts, as many of you do, is really ridiculous.(不定式作为先行词)
二、 作介词
As作为介词使用比较简单，一般可以理解为“作为……”
He travels to China as a tourist.
As a legal member of the organization, our company attended the conference.
The bomb was disguised as a package.
He works as an accountant.
You can use that glass as a vase.
三、 作连词
1.“当……时候”“随着……”——when while，引导时间状语从句
The girl dances as she sings on stage.两个动作交替进行
He looked behind from time to time as he went forward.
As time went on, she became increasingly mature.
2.表示原因“由于”“既然”，引导原因状语从句—since 常常表示一个显而易见的原因或者大家都知道的原因。
As you were out, I left a message.
As you are not feeling well, you may stay at home.
She may need help as she’s new here.
3.=in the way in which表示方式，引导方式状语从句
They did as I had asked.
She lost it ,just as I said she would.
You should speak English as Americans do.
4.表示“虽然”“尽管”，引导让步状语从句（常倒装）= although;
Happy as they were, there is something missing.
Child as he is , he knows much.
**As+adj/adv+as结构：“与……一样”,否定形式是not so/as +adj/adv+as
This movie is as exciting as that one.个是副词，第二个是连词
The dictionary is not so/as usefull as you think.
**若有times，twice，quarter等类似词时，要放在as前面
Your cup is twice as big as mine.
常用的短语：
As soon as possible
As+adj/adv+ as usual/before
As long as(引导条件状语从句)
As far as 就……而言；直到… 远到…
You’ll be accompanied as far as the border.
As far as I know, he was a policeman.
As well as:He grows flowers as well as vegetables.
As busy as a bee
As easy as ABC
As light as a feather
As for(regarding) sb./ as to sth.：As to tax, that will be deducted from your salary.
as if /as though:He pretended as if nothing had happened.
As it is:实际上，事实上considering the present situation, as things are
We were hoping to finish it by next week-as it is, it may be the week after.
As it were（used when a speaker is giving his or her own impression of a situation or expressing sth in a particular way):似乎，可以说是，实际上可以这么说
He grew up, as it were, in a in a different growing environment from others.（好像）
A friend is , as it were, a second self.可以说是
He became, as it were, a hero from a strange land.可以说是
As against: in contrast with 与……相比
They got 27% of the vote as against 32% at the last election.
