When和While的區(qū)別
1. when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。
They were sweeping the floor when the teacher came in.
老師進(jìn)來時(shí)（這一時(shí)刻），他們?cè)诓恋匕濉?br> While they were sweeping the floor，the teacher came in.
他們正擦地板時(shí)（這段時(shí)間），老師進(jìn)來了。

2. when 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。例如：
They were singing while we were dancing.

3. 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)，例如：
I am cooking while Jane is practicing.
我在做飯的時(shí)候簡(jiǎn)正在練習(xí)。
當(dāng)此句改變主從句的位置時(shí)，則用when引導(dǎo)。
When the teacher came in，we were talking.

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

和when引導(dǎo)的時(shí)間狀語從句主句用一般時(shí)（一般過去時(shí)）從句用進(jìn)行時(shí)（過去進(jìn)行）.while引導(dǎo)的從句要加延續(xù)性動(dòng)詞，而when 延續(xù)和短暫性動(dòng)詞都可以，所以when有包含while ，while可以用when替換。

6. 另外，when和while的區(qū)別還在于：while引導(dǎo)的時(shí)間狀語從句多用進(jìn)行時(shí)態(tài)，而when引導(dǎo)的時(shí)間狀語從句多用一般時(shí)態(tài)。
While they were talking , the bell rang.
正在他們談話的時(shí)候，上課鈴響了。
I was doing my homework when my mother came back home yesterday evening.
昨天晚上媽媽回家的時(shí)候，我正在做家庭作業(yè)。