as when while since的区别

as
副词 adv.
1.同样地,一样地
She is as tall as her mother.
她和她母亲一样高.
The dining room was twice as big as the Tom's.
这个餐厅比汤姆的餐厅大一倍.
This is as difficult a problem as you are likely to meet.
像这样的难题,你可能会碰到.
介词 prep.
1.(表示时间)当还是…的时候
As a schoolboy,he showed every sign of genius.
当他还是个小学生的时候,就显示出了天资聪慧.
2.(表示方式)以…的身份,以…资格,作为; 以…形式,以作为; 以…角色,扮演…角色; 如同,像
3.(表示结果)成为,看作,看成
We had better treat it as a joke.
我们最好把它当作玩笑.
4.(表示目的)为了,以…为目的
The dykes were built as a protection against the sea.
建筑堤坝是为了防止海水泛滥.
5.(表示举例)例如,诸如…之类的
We talked about such subjects as the weather.
我们谈论了诸如天气之类的话题.
连接词 conj.
1.在…期间,当…时候
I was coming in as he was going out.
我进来的时候,他正出去.
2.尽管,即使,虽然
Intelligent as you are,I suspect you will fail.
尽管你聪明,我猜想你会失败.
3.像…一样
4.由于,因为
As you weren't there I left a message.
因为你不在那里,我留了个信儿.
5.照…方式
6.正如；如同
when
ad.
1.(用作疑问副词)什么时候,何时
I'd like to know when they'll let him out.
我想知道他们什么时候放他.
When did you last see Margaret?
你上一次见到玛格丽特是什么时候?
2.(用作关系副词,引导关系从句)当...时
There were times when I didn't know what to do.
有些时候我不知道该怎么办才好.
conj.
1.当...时
John got engaged to her when travelling last winter.
去年冬天旅行时,约翰与她订了婚.
Don't get excited when you talk.
你说话时别激动.
2.既然,考虑到
How can he get the promotion when his boss dislikes him?
既然上司不喜欢他,那他怎么会获得提升呢?
3.虽然,然而
I had only fifteen dollars on me when the book I wanted cost twenty.
我身上只带了十五元钱,可是我想买的那本书定价二十元.
4.在那时,然后
pron.
1.什么时候,那时
Since when has she taught here?
她从什么时候开始在这儿教书的?
n.
1.(事件发生的)时间[the S]
while
KK:[]
DJ:[]
n.
1.一会儿,一段时间[S]
I'll be back in a while.
我一会儿就回来.
conj.
1.当...的时候,和...同时
She listened closely while he read the letter.
他读信时,她听得很仔细.
I'll take care of your children while you are away.
你不在时我会照顾你的孩子的.
We must strike while the iron is hot.
我们必须趁热打铁.
2.而,然而
I like tea while she likes coffee.
我喜欢喝茶,而她喜欢喝咖啡.
3.虽然,尽管
While I like the color of the hat,I do not like its shape.
虽然我喜欢这顶帽子的颜色,但我不喜欢它的形状.
4.只要
vt.
1.消磨(时光),轻松地度过[(+away)]
He whiled away the whole afternoon watching TV.
他看电视消磨了一个下午.
since
KK:[]
DJ:[]
ad.(常用于现在完成时或过去完成时)
1.此后;从那时到现在
She left school three years ago and has worked as a nurse ever since.
她三年前毕业,从那时起便一直当护士.
2.之前,以前
prep.
1.(常用于现在完成时或过去完成时)自...以来,从...至今
I haven't heard from him since last year.
我自去年以来未曾收到过他的信.
conj.
1.(常用于现在完成时或过去完成时)自...以来,从...至今
It's been ten years since they married.
他们结婚到现在已经十年了.
She has been living a hard life since her husband died.
她自从丈夫死后,一直过着艰苦的生活.
2.既然;因为,由于
He must have taken the book since it isn't here.
他一定是把书拿走了,因为书已不在这里了.
Since it is so hot,let's go swimming.
既然天气这么热,我们去游泳吧

as 后不是跟从句，而是不定式

As引导时间状语从句，意思是：随着，表示动作同时发生，通常放在句首。
when，while和as引导时间状语从句
when引导的时间状语从句既可表示“点时间”，也可表示“段时间”；
while只能表示“段时间”；
as只能表示“点时间”。
when引导的从句的动作和主句的动作可以同时发生，也可以先后发生；
as，while则强调主句和从句...

as when while 意思相近，都可以表示“当……时候”
as 后不是跟从句，而是不定式；
when和while后面跟的是从句，有动词。
since 表示“自……以来”