1、作介词。
1. he spoke as a teacher. 他作为老师发言&他以老师的身份发言（表“作为”）
2. he spoke like a teacher. 他讲话很像是老师。
3. 表示“当某人是(某身份)时。例如：
as a child, she was sent to three different countries. 她儿时去过3个不同的国家。
4.表示“因某人是(某身份)”，例如：
as a gardener, hell take care of all flowers.因作为1个园丁，他将会照顾所有的花朵。
5.表示“作为，当作”，例如：
i found a job as a teacher. 我找了1份教师的工作。(take sb. as/treat sb. as...
famous as=be known as表“以。身份而著名”，注意与be famous for=be known for表“因。而闻名“的区别。
he is known as a successful lawyer.
qingdao is known for its beautiful summer.
2、用于固定词组。
long as表“只要”
as long as we dont lose heart,well find a way to overe the difficulty.只要我们不灰心，我们就能找到克服困难的办法。
ill never forget that as long as i am living.这事我至死也不会忘记。
备注：keep it as long as you like.你能把它保留多久，就保留多久。（还可作“..之久“）
far as表“据…, 就… ”
as far as i know, he will be away for three months.据我所知， 他将离开3个月。
as to do=in order to do表“为了”但so as to do只能放句中。
they started early so as to catch the first bus.他们很早就出发了，以便能赶不上头班车。
to do表"如此。以至于“相当于so that引导的“结果状语从句”
you are so kind as to show me the way.你真好，给我指路。
only…but…as well=not only…but also表“不但。而且。”
as well as=not only…but also
not only you but also your wife is friendly to me.(动词跟后面的wife）
your wife as well as you is friendly to me.（动词跟前面的wife)
不但你而且你妻子也对我很好。
注意：you look as well as you were./you look as well as before.
well表“又，也”常用于句尾（无需逗号分开）
the skirt is small for me as well.这条裙子对于我来说也小了。
as well=might as well表“还不如，也好”相当于=had better
i may as well go home.我还是回家好了。
usual表“如平常”
i went to school as usual.我像平常1样去上学。
a matter of fact=in fact表“其实；实际上”
as a matter of fact, i’m very fond of housework. 其实，我很喜欢做家务。
a result表“结果，因此” (发生某种情况)
as a result, he had to le**e.结果他只得离开。
而as a result of表“由于。结果“，as a result of carelessness, he drove into a lamppost.
3、作连词引导状语从句。
1. 引导时间状语从句。
as与when，while都是引导时间状语从句的从属连词，含义都是"当……的时候"。但它们有区别：
1). when作“当……的时候”解，可以指较短的(1点)时间，也可指1段时间。从句的动作可以与主句的动作同时发生，也可以先于主句的动作发生。例如：
john was h**ing his dinner when i saw him. 当我看到约翰的时候，他正在吃饭。
she can write only when the baby is asleep. 只有婴儿睡着的时候，她才能写作。
2). while常表示1段较长的时间或1个过程，强调主句谓语动词与从句谓语动词同时发生或在从句动作过程中发生。例如：
we must strike while the iron is hot. 要趁热打铁。
while we were reading, the teacher came in. 我们正在读书的时候，老师走了进来。
3). 但属下列情形时，只用as, 而不用when或while。
1 用于表示同1个人的两种动作交替进行，指“1边……,1边……”例如：
the girl dances as she sings on the stage.那个女孩在舞台边唱歌边跳舞。
he looked behind from time to time as he went forward. 当他朝前走时，不时地向后看。
2 表示两个同步发展的动作或行为，译为“随着……”例如：
as time went on / by, she became more and more worried. 随着时间的流逝，她变得越来越焦虑。
as he grew older, he became more intelligent. 随着他年龄的增长，他变得更有才智了。
3 表示两个短促行为或事件几乎同时发生。例如：
i thought of it just as you opened your mouth. 恰好在你开口时，我想到了它。
just as the flying worm hit her face, she g**e a loud cry. 恰巧在飞虫撞到她脸上时，她大哭起来。
4短语：as soon as表示"1..就。"
he will write to me as soon as he gets the letter.他1接到信，就会给我写回信。
2. 引导原因状语从句。
as，because，since都可以表示因果关系，连接原因状语从句，含义是“因为，由于”，但它们有区别：because表示的语气最强；as1般放在句首，语气较弱，较口语化；since常常用在书面语中，表示多为对方已知的、或稍加分析便可得知的原因，有时可译作“既然”。例如：
i do it because i like it. 我做这件事是因为我喜欢。
since many of the customers work during the day, billy has to collect the money at night. 因为许多顾客白天上班，所以毕利只好晚上去收钱。
as you werent there i left a message.因为你不在那里， 我留了个信儿。
3. 引导让步状语从句。
as与although (或though)，however (或no matter how)等都可以引导让步状语从句，含义是“虽然，尽管”，但它们有区别：although语气稍正式些，可放在句首，也可放在句中，主句中不能再用 but，但可以用yet;as所表示的语气较强，引导的让步状语从句用倒装语序；however引导让步状语从句时，它的后面可跟形容词或副词，也要用倒装语序。例如：
although they are poor they are happy. 虽然他们很穷，但很快乐。
angry as he was, he managed to speak calmly. 虽然他很生气，但是他讲话很平静。
however hard the question is, he can answer it. 不管问题有多难他都能回答。
注意：当as引导让步状语从句时，句子的倒装语序有以下3种形式：
1). 形容词或副词+as+主语+连系动词be或实义动词。例如：
rich as he is, he never spends a cent on clothes. 虽然他很富有，但他从不花1分钱在衣服上。
much as i admire his courage, i don’t think he acted wisely. 我虽然佩服他的勇气，但我认为他这样做是不聪明的。
2). 名词+as+主语+连系动词be (注意句首的名词不带冠词)。例如：
child as he is, he knows a lot. 尽管他是个孩子，但懂很多事情。
boy as he was, he was chosen king. 尽管他还是个孩子，但却被立为国王。
3). 实义动词+as+主语+助动词[如果没有助动词，则要加上1个do(does或did)]。例如：
try as he may, he never succeeds. 尽管他很努力，但总是不成功。
change your mind as you will, you will gain no additional support. 即使你改变主意，你也不会得到另外的支持。
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