as, when, while的區(qū)別：as, when, while都表示主、從句的動(dòng)作或狀態(tài)同時(shí)發(fā)生，但三者意義不相同。

1. as和when引導(dǎo)的從句既可表示一點(diǎn)時(shí)間，也可表示一段時(shí)間，從句中的謂語動(dòng)詞既可以是持續(xù)性動(dòng)詞，也可以為短暫性動(dòng)詞，經(jīng)常可以互換使用;

His mother called him Robbie when he was a baby.

2. while引導(dǎo)的從句通常表示一段時(shí)間，從句中宜用持續(xù)性動(dòng)詞作謂語。

I’ll look after the children while you are making dinner.

當(dāng)從句中的謂語動(dòng)詞為持續(xù)性動(dòng)詞時(shí)，as, when, while可以通用，如：

Mother was worried because little Alice was ill, especially as / when / while father was away in France.媽媽擔(dān)心，因?yàn)樾“愃疾×耍貏e是當(dāng)父親遠(yuǎn)在法國的時(shí)候。

如果從句和主句要表示一個(gè)人的兩個(gè)動(dòng)作交替進(jìn)行或同時(shí)完成時(shí)，則多用as，可譯為“一邊......，一邊......”。

例如：

He looked behind from to time as he went.他一邊走，一邊不時(shí)地往后看。

As time goes on, it’s getting warmer and warmer..隨著時(shí)間的推移，天氣變得越來越暖了。

I thought of it just as you opened your mouth.你一張嘴我就知道你要說什么。(若表示兩個(gè)短促動(dòng)作幾乎同時(shí)發(fā)生時(shí)，用as的場合多于when.)

當(dāng)主從句之間表示轉(zhuǎn)折或?qū)Ρ汝P(guān)系時(shí)，多用while, 不用as或when。如：

She thought I was talking about her daughter, while in fact, I was talking about my daughter.她以為我在談?wù)撍畠海聦?shí)上，我在談?wù)撐业呐畠骸?/p>

如果表示從句的動(dòng)作在主句的動(dòng)作“之前”或“之后”發(fā)生時(shí)，多用when(=after), 不用as或 while。此外，when還含有“at that moment”的意思(= and then)，引起的句子不能放在句首，也不能用as, while來替換。例如：

He was about to leave when the telephone rang.他正要離開，忽然電話鈴響了。

We were watching TV when suddenly the lights went out.我們正在看電視，突然燈滅了。

They had just arrived home when it began to rain.他們剛到家，天就開始下雨了。