As的用法小结（一）、as作连词的用法:1.作“在…期间，当…的时候”引导时间状语从句.注意与when、while的用法区别。
①下列情形时,只用as, 而不用when或while。
1)用于表示同一个人的两种动作交替进行,指一边----一边. 如:The girl sings as she goes to school.He looked behind occasionally as he went forward in the forest.2)表示两个同步发生的动作或行为,意思是随着…的发展.如:As time went on / by, she became more and more beautiful.As children get older, they become more and more interested in everything.3)表示两个短暂行为或事情几乎同时发生.如:I watched her as she read the book.I thought of it just as you opened your mouth.Just as the flying worm hit her face, she gave a loud cry.4)接名词表示某一个年龄段时.如:As a young man, he was active in sports.As a little boy (When he was a little boy) he began to learn to play the piano.②when作"当……的时候"解,可以指较短的(一点)时间,也可指一段时间。
如:When I was at college, I could speak several foreign languages.When the clock struck twelve, I had slept for 2 hours.I was wandering through the street when I caught sight of a tailor’s shop有意料之外的意思③while常表示一段较长的时间或一个过程,强调主句谓语动词与从句谓语动词同时如:Work while you work. Play while you play.Strike while the iron is hot趁着2. As =Since 作"既然"、"由于"解,常用来表示已为人们所知或显而易见的原因或理由。
如: As he’s been ill for ages, I will help him.As / Since you're not feeling well, you may stay at home.As he wasn't ready, we went without him.3. As =in the way that作"像"、"按照……的方式"解,引导方式状语从句。
如: Do as I told you. Remember, you must do everything as I do. Take the medicine as directed. Maglev trains don’t make much noise, as planes do. When at Rome，do as Romans do．入乡随俗As in your country，we grow wheat in the north and rice in the South.4. 用于as--- as或not / so/ as ---- as中,前一个as是副词,后一个as是连词,引导比较状语从句。
如:They helped the old as much as possible.I don't speak English so/ as well as she does.5. 表示虽然,尽管等,引导让步状语从句,常用倒装语序,模式为: adj. /adv. / n.+as +主语+谓语+主句。
如: Tired as they were, they walked on. Child as he is ，he knows a lot．Fast as he ran，he didn't catch the bus．Much as I respect him, I won’t do as suggests. Try as you may, you might fail again Try as he might，Tom could not get out of the difficulties．6. 表示也------一样。
She is a doctor, as was her husband.（二）、as作关系代词,引导定语从句,表示正如,这一点.如:He is very careful, as we all know. As is well-known, Taiwan belongs to China.另外,当先行词被the same, such, so等词修饰时,常用as来引导定语从句。
如:Such a clever girl as she can learn anything quickly.He wished to be such a man as Lei Feng was．I was reading the same book as he bought yesterday. This book is not such as I expectNote: He took the police back to the same place where he witnessed the robbery（三）、as作介词的用法.1.表示好像。
如:He dressed as a policeman. They got united as one man．2. 表示作为当作。
如：I found a job as a guide.3. 当某人是某身份时。
如：As a child , she was sent to abroad.4. as引导的介词短语大多用作状语,as译为"作为";少数情况可引起宾语补足语。
如:As a Party member, I'll take the lead in everything. (状语) She works as a model. (状语) She has me as one of her best friends.(引起宾语补足语)（四）、作副词的用法1 表示与------等同。
如：This dress is twice as expensive as that one.2 像，如等。
As before, he remained unmoved. He doesn't speak English as／so fluently as you．（3）英语中有很多表示比较的成语。
as black as coal as blind as a bat as brave as a lion as bright as day as busy as a bee as cold as ice as easy as ABCas fat as a pig as hot as fire as light as air ／a feather as like as two peas ／beans as poor as a church mouse as rich as a Jew as sound as a bell状况极佳;十分健康as fit as a fiddle as strong as a horse as stupid as a donkey as sweet as honey ／sugar as white as snow as red as blood as bright as a button as wise as Solomon(五）含as的固定词组的用法1.As soon as I get to Beijing，I'll write to you．我一到北京，就给你写信。
2．as／so long as作“只要”解，eg；As／So long as you study hard，you'll make progress．比较：I've waited as long as two hours．我一直等了整整两小时。
3．as if／though常用来引导方式状语从句，作“好像，仿佛”解。
如果从句中讲的是非真实情况，则用虚拟语气。
eg：She loves the child as if／though he were her own．As if／though也可用来引导表语从句，常用在“It looks／seems．．．+as if／though”句型结构中。
It looks to me as if／though it is going to clear up．It seems as if／though he knew nothing about it. You look as though you slept badly.4．as to作“关于，至于”解。
eg；There is no doubt as to his honesty．5．as much／many as“多达…”，“达到…之多”eg：He can earn as much as 5000 dollars a month．6．As／So far as I know，he will come here next Monday．据我所知，比较：We might go as far as the school and back．我们可以走到学校那边，然后回来。
7．She died as a direct result of the accident．表示“由于．．．的结果”。
8，as well为“也，还”之意。
eg：Come early，and bring your brother as well．9．so as to，表示目的so．．．as to表示结果。
eg：He studied hard so as to pass the exam．他努力学习以便通过考试。