when while 區(qū)別

　　when 當(dāng)什么時(shí) 可表瞬間 事情可同時(shí) 或者先后發(fā)生

　　例子

　　it was snowing when we got to the airport 我們到機(jī)場(chǎng)時(shí) 天在下雪(先后順序)

　　while 用于相伴發(fā)生的 同時(shí)進(jìn)行

　　例子

　　some students were reading while others were writing

　　有些學(xué)生在讀書 有些在寫.

　?、賥hen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。

　?、趙hen 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。

　?、塾蓋hen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.

　?、躻hen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(zhǎng)得很結(jié)實(shí)，而他弟弟卻很瘦弱