急需知道。

when 和while的用法區(qū)別
兩者的區(qū)別如下：

①when是at or during the time that, 既指時(shí)間點(diǎn)，也可指一段時(shí)間；

while是during the time that，只指一段時(shí)間，因此when引導(dǎo)的時(shí)間狀語從句中的動(dòng)詞可以是終止性動(dòng)詞，也可以是延續(xù)性動(dòng)詞，而while從句中的動(dòng)詞必須是延續(xù)性動(dòng)詞。

②when 說明從句的動(dòng)作和主句的動(dòng)作可以是同時(shí)，也可以是先后發(fā)生；while 則強(qiáng)調(diào)主句的動(dòng)作在從句動(dòng)作的發(fā)生的過程中或主從句兩個(gè)動(dòng)作同時(shí)發(fā)生。

③由when引導(dǎo)的時(shí)間狀語從句，主句用過去進(jìn)行時(shí)，從句應(yīng)用一般過去時(shí)；如果從句和主句的動(dòng)作同時(shí)發(fā)生，兩句都用過去進(jìn)行時(shí)的時(shí)候，多用while引導(dǎo)，如：

a. When the teacher came in, we were talking.

當(dāng)此句改變主從句的位置時(shí)，則為：

While we were talking, the teacher came in.

b. They were singing while we were dancing.

④when和while 還可作并列連詞。when表示“在那時(shí)”；while表示“而，卻”，表對(duì)照關(guān)系。如：

a. The children were running to move the bag of rice when they heard the sound of a motor bike.

孩子們正要跑過去搬開那袋米，這時(shí)他們聽到了摩托車的聲音。

b. He is strong while his brother is weak.
他長得很結(jié)實(shí)，而他弟弟卻很瘦弱。