請問as,while,when有何分別?

as:
1. 跟...一樣地,同樣地
Sam is as rich as Alexander.
山姆像亞歷山大一樣富有。
2. 如同;例如
Such animals as foxes and squirrels have bushy tails.
有些動物,如狐和松鼠,有蓬鬆的尾巴。

1. 作為,以...的身分
She works as an interpreter in that company.
她在該公司裡擔任翻譯員。
2. 當作
She didn't think much of him as a painter.
她對他作為一位畫家評價不高。
3. 像;如同
The old woman was dressed as a young lady.
這位老婦人打扮得像一位年輕人。

1. 像...一樣;依照;像
You ought to do as Paul tells you.
你應按照保羅吩咐的做。
The work is not so difficult as you imagine.
這工作不像你想像的那麼困難。
2. 當...時
As she left the room she remembered that book.
她離開房間時想起了那本書。
3. 隨著
As the sun rose the fog dispersed.
太陽一出來,霧隨之消失。
4. 因為
We didn't know what to do as we were just visiting there.
我們不知道該怎麼辦,因為當時我們僅僅在那裡作訪問。
5. 雖然
Tired as he was, he sat up late.
他雖然疲倦,可仍然很晚才睡。

1. (與such, the same, as等連用,引導關係子句)與...相同的事物(或人)
He has earned as much money as I have.
他賺的錢和我賺的一樣多。
She felt just the same as he did.
她和他的感受相同。
There is a general rise in prices such as occurred in the late 60's.
物價普遍上漲,跟六十年代末一樣。
2. (引導子句,對前述內容作補充)本情況,該事實
She has married again, as was expected.
她已再婚,這是意料中的事。
We are tired, as anyone can see.
我們累了,這是有目共睹的。

while:.
1. 一會兒,一段時間[S]
I'll be back in a while.
我一會兒就回來。
conj.
1. 當...的時候,和...同時
She listened closely while he read the letter.
他讀信時,她聽得很仔細。
I'll take care of your children while you are away.
你不在時我會照顧你的孩子的。
We must strike while the iron is hot.
我們必須打鐵趁熱。
2. 而,然而
I like tea while she likes coffee.
我喜歡喝茶,而她喜歡喝咖啡。
3. 雖然,儘管
While I like the color of the hat, I do not like its shape.
雖然我喜歡這頂帽子的顏色,但我不喜歡它的形狀。
4. 只要
vt.
1. 消磨(時光),輕鬆地度過[(+away)]
He whiled away the whole afternoon watching TV.
他看電視消磨了一個下午。

when:1. (用作疑問副詞)什麼時候,何時
I'd like to know when they'll let him out.
我想知道他們什麼時候放他。
When did you last see Margaret?
你上一次見到瑪格麗特是什麼時候?
2. (用作關係副詞,引導關係子句)當...時
There were times when I didn't know what to do.
有些時候我不知道該怎麼辦才好。
conj.
1. 當...時
John got engaged to her when travelling last winter.
去年冬天旅行時,約翰與她訂了婚。
Don't get excited when you talk.
你說話時別激動。
2. 既然,考慮到
How can he get the promotion when his boss dislikes him?
既然上司不喜歡他,那他怎麼會獲得提升呢?
3. 雖然,然而
I had only fifteen dollars on me when the book I wanted cost twenty.
我身上只帶了十五元錢,可是我想買的那本書定價二十元。
4. 在那時,然後
pron.
1. 什麼時候,那時
Since when has she taught here?
她從什麼時候開始在這兒教書的?
n.
1. (事件發生的)時間[the S]