when和while的區(qū)別
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(yǔ)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(shuō)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(guò)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(yǔ)從句,主句用過(guò)去進(jìn)行時(shí),從句應(yīng)用一般過(guò)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(guò)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(guò)去搬開(kāi)那袋米,這時(shí)他們聽(tīng)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.
具體你可以參考這一段.
when,while,as引導(dǎo)時(shí)間狀語(yǔ)從句的區(qū)別
when,while,as顯然都可以引導(dǎo)時(shí)間狀語(yǔ)從句,但用法區(qū)別非常大.
一、when可以和延續(xù)性動(dòng)詞連用,也可以和短暫性動(dòng)詞連用；而while和as只能和延續(xù)性動(dòng)詞連用.
① Why do you want a new job when youve got such a good one already?（get為短暫性動(dòng)詞）你已經(jīng)找到如此好的工作,為何還想再找新的?
②Sorry,I was out when you called me．（call為短暫性動(dòng)詞）對(duì)不起,你打電話時(shí)我剛好外出了.
③Strike while the iron is hot．（is為延續(xù)性動(dòng)詞,表示一種持續(xù)的狀態(tài)）趁熱打鐵.
④ The students took notes as they listened．（listen為延續(xù)性動(dòng)詞）學(xué)生們邊聽(tīng)課邊做筆記.
二、when從句的謂語(yǔ)動(dòng)詞可以在主句謂語(yǔ)動(dòng)作之前、之后或同時(shí)發(fā)生；while和as從句的謂語(yǔ)動(dòng)作必須是和主句謂語(yǔ)動(dòng)作同時(shí)發(fā)生.
1．從句動(dòng)作在主句動(dòng)作前發(fā)生,只用 when.
①When he had finished his homework,he took a short rest．（finished先發(fā)生）當(dāng)他完成作業(yè)后,他休息了一會(huì)兒.
②When I got to the airport,the guests had left．（got to后發(fā)生）當(dāng)我趕到飛機(jī)場(chǎng)時(shí),客人們已經(jīng)離開(kāi)了.
2．從句動(dòng)作和主句動(dòng)作同時(shí)發(fā)生,且從句動(dòng)作為延續(xù)性動(dòng)詞時(shí),when,while,as都可使用.
①When ／While ／As we were dancing,a stranger came in．（dance為延續(xù)性動(dòng)詞）當(dāng)我們跳舞時(shí),一位陌生人走了進(jìn)來(lái).
②When ／While ／As she was making a phonecall,I was writing a letter．（make為延續(xù)性動(dòng)詞）當(dāng)她在打電話時(shí),我正在寫信.
3．當(dāng)主句、從句動(dòng)作同時(shí)進(jìn)行,從句動(dòng)作的時(shí)間概念淡化,而主要表示主句動(dòng)作發(fā)生的背景或條件時(shí),只能用 as.這時(shí),as常表示“隨著……”；“一邊……,一邊……”之意.
① As the time went on,the weather got worse．（as表示“隨著……”之意）
② The atmosphere gets thinner and thinner as the height increases．隨著高度的增加,大氣越來(lái)越稀薄.
③As years go by,China is getting stronger and richer．隨著時(shí)間一年一年過(guò)去,中國(guó)變得越來(lái)越富強(qiáng)了.
④The little girls sang as they went．小姑娘們一邊走,一邊唱.
⑤The sad mother sat on the roadside,shouting as she was crying．傷心的媽媽坐在路邊,邊哭邊叫.
4．在將來(lái)時(shí)從句中,常用when,且從句須用一般時(shí)代替將來(lái)時(shí).
①You shall borrow the book when I have finished reading it．在我讀完這本書后,你可以借閱.
②When the manager comes here for a visit next week,Ill talk with him about this．下周,經(jīng)理來(lái)這參觀時(shí),我會(huì)和他談?wù)劥耸?
三、when用于表示“一……就……”的句型中（指過(guò)去的事情）.
sb．had hardly（＝scarcely） done sth．when．．．＝Hardly ／ Scarcely had sb．done sth．when．．．
①I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／ Scarcely had I closed my eyes when someone knocked at the door．我剛一閉上眼,就有人在敲門了.
②I had hardly ／scarcely entered my room when the telephone rang．＝Hardly ／Scarcely had I entered my room when the telephone rang．我剛一走進(jìn)房門,電話就響了