A when
　　when 與 while 用法解析
　　連接詞when與while是一對(duì)常與過(guò)去進(jìn)行時(shí)合作的twins.但正如世界上沒(méi)有兩片完全相同的樹(shù)葉一樣,when與while在有著某些相似之處的同時(shí),彼此也各有一些區(qū)別于對(duì)方的截然不同的“獨(dú)特個(gè)性”.Do you want to know the differences between them?請(qǐng)看——
　　● when 解析版
　　〔引導(dǎo)時(shí)間狀語(yǔ)從句〕具體地說(shuō),它有以下幾種含義：
　　1．表明一個(gè)動(dòng)作發(fā)生的時(shí)候,另一個(gè)動(dòng)作正在進(jìn)行之中.例如：
　　When the teacher came into the classroom ,we were reading English．當(dāng)老師走進(jìn)教室時(shí),我們正在讀英語(yǔ).
　　2．表明當(dāng)某一動(dòng)作正在進(jìn)行時(shí),另一動(dòng)作發(fā)生了.如：
　　When Kate was flying a kite,she found a wallet lying on the ground．凱特正在放風(fēng)箏時(shí),她發(fā)現(xiàn)地上有個(gè)錢(qián)包.
　　〔特別提示〕當(dāng)when從句放在主句之后時(shí),它更強(qiáng)調(diào)某一動(dòng)作的突然性,此時(shí)的when相當(dāng)于and then,and suddenly,just at that time.如；
　　1．We were watching TV when the telephone rang．（＝We were watching TV and suddenly the telephone rang．）我們正在看電視,（突然）電話(huà)鈴響了.
　　試比較：When we were watching TV, the telephone rang．我們正在看電視時(shí),電話(huà)鈴響了.
　　2．The boys were playing football when it began to rain．男孩子們正在踢球時(shí),（不料）開(kāi)始下雨了.
　　3．I was taking a walk when I came across Lily．我正在散步時(shí),（沒(méi)想到）遇見(jiàn)了莉莉.
　　特別是主句中有just,或when從句中有suddenly時(shí),這種突然性更為明顯、強(qiáng)烈.例如：
　　4．He was just falling asleep when he heard someone shout,“Stop the thief!”他剛要入睡,突然聽(tīng)到有人喊：“抓賊!”
　　5．We were doing our homework at school last night when the lights went out．昨天晚上我們正在學(xué)校寫(xiě)作業(yè)時(shí),燈（突然）滅了.
　　〔相關(guān)鏈接〕when引導(dǎo)的狀語(yǔ)從句除了上述意義之外,也常具有其他一些含義：
　　1．一……就……（＝as soon as）
　　We will stand up when the teacher comesin．老師一進(jìn)來(lái)我們就起立.
　　2．雖然；然而；可是（＝although）
　　We had only five boxes when we needed eight．我們需要八個(gè)箱子,可是只有五個(gè).
　　3．每當(dāng)……（＝whenever）
　　It is always very hot here when it is summer．每當(dāng)夏季,這兒總是很熱.
　　4．既然（＝since,as）
　　Why did you come here on foot when you know you should come by bike?既然你知道該騎自行車(chē)來(lái),你為何還要步行呢?
　　● while 解析版
　　while引導(dǎo)狀語(yǔ)從句,有以下兩種含義：
　　1．表示某個(gè)動(dòng)作正在進(jìn)行的同時(shí),另一動(dòng)作也在進(jìn)行之中,這時(shí)主從句都用進(jìn)行時(shí)態(tài),有對(duì)同類(lèi)的兩個(gè)動(dòng)作進(jìn)行對(duì)比的意味.如：
　　While I was playing the piano,she was dancing．我在彈鋼琴,她在跳舞.
　　While Jim is picking apples,Kate is carrying apples to the truck．吉姆正在摘蘋(píng)果,凱特正在把蘋(píng)果搬到卡車(chē)上去.
　　2．表示某個(gè)動(dòng)作正在進(jìn)行時(shí),又發(fā)生了另一動(dòng)作（該動(dòng)作用一般過(guò)去時(shí)）.如：
　　While I was reading,I fell asleep．我讀著讀著就睡著了.
　　While we were swimming in the river,we saw a fish jump out of the water．我們正在河中游泳時(shí),看見(jiàn)一條魚(yú)躍出了水面.
　　〔相關(guān)鏈接〕
　　while還有以下幾種常見(jiàn)用法：
　　1．只要（＝as long as）
　　There will be life while there is water and air．只要有空氣和水,就會(huì)有生命.
　　2．而；然而〔表示對(duì)比〕
　　He is a driver while I'm a teacher．他是司機(jī),而我是老師.
　　3．雖然（＝although）；盡管〔表示讓步〕
　　While I see what you say,I can't agree with you．雖然我能理解你說(shuō)的話(huà),但是我不能同意你.
　　4．用作名詞,表示“一會(huì)兒或一段時(shí)間”,常與a,the或this等連用.如：
　　Just wait a while and then I will help you．等一下,我會(huì)來(lái)幫你的.
　　Where have you been all this while?這一陣子你一直都在哪兒?
　　● when 與 while 區(qū)別版
　　綜上所述,我們可以看出when與while本質(zhì)的區(qū)別在于：when既可以指某一點(diǎn)時(shí)間,也可以指某一段時(shí)間,其從句謂語(yǔ)動(dòng)詞表示的動(dòng)作既可以是瞬間性的、非延續(xù)性的,也可以是延續(xù)性的；while指一段時(shí)間,從句中的謂語(yǔ)動(dòng)詞必須是延續(xù)性的.即：指一段時(shí)間時(shí),when可用while來(lái)代替；指一點(diǎn)時(shí)間時(shí),when不能用 while來(lái)代替.試比較：
　　When he woke up,it was eight o'clock．（√）
　　While he woke up,it was eight o'clock．（×）
　　When I was waiting for a bus,I met her．（√）
　　While I was waiting for a bus,I met her．（√）
　　●練習(xí)版 Can you say the following sentences in English?
　　1．當(dāng)我們到達(dá)火車(chē)站時(shí),天正下著雪.
　　______________________________
　　2．孩子們正在做游戲,突然鈴響了.
　　______________________________
　　3．爸爸在洗車(chē)時(shí),媽媽在做飯.
　　______________________________
　　4．琳達(dá)正在跑步時(shí)傷了自己的左腿.
　　______________________________
　　5．我們?cè)谖靼矔r(shí),每天見(jiàn)面.
　　______________________________
　　Key:
　　1．When we got to the train station,it was snowing．
　　2．The children were playing games when the bell rang．
　　3．While dad was washing his car,mum was cooking．
　　4．When ／While Linda was running,she hurt her left leg．
　　5．When ／While we were in Xi'an,we met every day． when和while引導(dǎo)的時(shí)間狀語(yǔ)從句與這一時(shí)態(tài)連用.所以區(qū)別when和while的用法成了這一單元的難點(diǎn). （一）、when,while都有“當(dāng)……時(shí)候”的意思.when既可表示某一點(diǎn)時(shí)間,也可以表示某一段時(shí)間 .在when引導(dǎo)的時(shí)間狀語(yǔ)從句中,其謂語(yǔ)動(dòng)詞可以是延續(xù)性的,也可以是非延續(xù)性的,可與主句中的謂語(yǔ)動(dòng)詞同時(shí)發(fā)生,也可在其后發(fā)生. 例如： 1、I was just reading a book when she came into my room. 她走進(jìn)我房間時(shí),我正在看書(shū). 2、Were you writing when the teacher came in? 老師進(jìn)來(lái)的時(shí)候,你在寫(xiě)信嗎? 3、When he was a child he was always trying out new ideas. 他小時(shí)候就常常試驗(yàn)一些新的設(shè)想. （二）、while只能表示某一段時(shí)間,不能表示某一點(diǎn)時(shí)間.在while引導(dǎo)的時(shí)間狀語(yǔ)從句中,其謂語(yǔ)動(dòng)詞只能是延續(xù)性的,而且也只能與主句中的謂語(yǔ)動(dòng)詞同時(shí)發(fā)生或存在. 例如： 1、While Jim was mending his bike, Lin Tao came to see him. 正當(dāng)吉姆修自行車(chē)時(shí),林濤來(lái)看他. 2、You can’t do your homework while you’re watching TV. 你不能一邊看電視一邊做家庭作業(yè). （三）、另外,when和while的區(qū)別還在于：while引導(dǎo)的時(shí)間狀語(yǔ)從句多用進(jìn)行時(shí)態(tài),而when引導(dǎo)的時(shí)間狀語(yǔ)從句多用一般時(shí)態(tài). 例如： 1、While they were talking , the bell rang. 正在他們談話(huà)的時(shí)候,上課鈴響了. 2、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)