when与while的区别[1].doc

When和While的区别 when是at or during the time that, 既指时间点，也可指一段时间，while是during the time that，只指一段时间，因此when引导的时间状语从句中的动词可以是终止性动词，也可以是延续性动词，而while从句中的动词必须是延续性动词。 when 说明从句的动作和主句的动作可以是同时，也可以是先后发生；while 则强调主句的动作在从句动作的发生的过程中或主从句两个动作同时发生。 由when引导的时间状语从句，主句用过去进行时，从句应用一般过去时；如果从句和主句的动作同时发生，两句都用过去进行时的时候，多用while引导，如： a. When the teacher came in, we were talking. 当此句改变主从句的位置时，则为： While we were talking, the teacher came in. b. They were singing while we were dancing. when和while 还可作并列连词。when表示“在那时”；while表示“而，却”，表对照关系。如： a. The children were running to move the bag of rice when they heard the sound of a motor bike. 孩子们正要跑过去搬开那袋米，这时他们听到了摩托车的声音。 b. He is strong while his brother is weak. 他长得很结实，而他弟弟却很瘦弱。since和once用法如下，不易弄混since prep.自. 以来, .以后since liberation解放以来习惯用语ever since从那时起, 一直到现在long since好久以前, 早已not long since就在不久since then其后, 从此一直习惯用语 | 词性变化 | 参考词汇 | 更多.近/反义词现代英汉词典基本解释since prep.自以来； 自以后I have been there many times since the war.自那次战争以来，我曾去该地多次。Since then, he has developed another bad habit.自那以后,它养成了另一种环习惯。Since then, they have been trying to find out how the fire began.自那时以来,他们一直在设法查明起火的原因。词性变化conj.自以后； 自以来What have you been doing since I last saw you?自我上次和你见面以后，你在做什么？既然；因 为Since you ask, I will tell you.你既然问，我就告诉你。Since many of the customers work during the day, Billy has to collect the money at night.因为许多顾客白天上班,所以毕利只好晚上去收钱。adv.其后，后来At first he refused but since has accepted.他最初拒绝，但后来接受了。We have been friends ever since.自此以后我们一直是朋友。The fish, which has since been sent to a museum where it is being examined by a scientist, is called an oarfish.这条后来被送到一个博物馆,在那里接受一位科学家的观察、研究的鱼,名叫皇带鱼。以前How long since is it?那是在多久以前？习惯用语 | 词性变化 | 参考词汇 | 更多.近/反义词简明英汉词典基本解释since adv.以后, 后来, 以前prep.自从, 自.以来conj.自.以后, 自.以来, 因为, 既然习惯用语 | 词性变化 | 参考词汇 | 更多.近/反义词七国语言英汉公共大词典基本解释since以来;由于;自从例句since liberation从解放以后since May自五月以来Since August.8月份我就来了。Ever since yesterday.从昨天开始。since last Saturday从上星期六以来once adv.一次曾经; 从前一旦; 一度用于否定句一次也(不); 完全(不)乘以一; (亲属间行辈上)小一辈; (程度上)相差无几once a year一年一次a once powerful nation曾很强盛的国家a cousin once removed堂表兄弟姊妹的孩子If the facts once become known, he will be punished.事实一旦公开, 他就要受到惩罚。I couldnt once understand what he meant.我完全不懂他的意思。Once one is one.一一得一。习惯用语all at once突然; 同时at once立刻, 马上; 同时every once in a while美偶而for this once (=for once, just for once)就这一次; 破例一回if once (=when once)一旦more than once不止一次, 多次not once一次也不once again再一次once and again一再, 再三once and away一劳永逸; 限此一次; 断然, 爽快once for all一劳永逸; 永久地; 彻底地once in a while有时, 间或, 偶而once more再一次once again再一次once or twice一两次; 有时, 偶尔once over lightly从头到尾马马虎虎地once too often又(多了)一次习惯用语 | 词性变化 | 参考词汇 | 更多.近/反义词现代英汉词典基本解释once adv.一次，一回I go to see a film once a week.我每周看一场电影。Once a month, he has to collect money from his customers.每月一次,他得去向顾客收钱。Once a year a race is held for old cars.每年举行一次旧式小汽车比赛。Attention please, Ill repeat the question once more.请注意我把问题再重复一遍。从前； 曾经She once knew him.她以前认识他。Once, however, Big Ben failed to give the correct time.不过,有一次大本钟报错了时间。A good editor never once leaves a misprint uncorrected.一个好编辑决不会放过一个印刷错误。It once seemed inconceivable to everyone that men should travel to the moon.人们一度认为,人飞上月球似乎是不可想象的。词性变化conj.一旦；一就Once printed, this dictionary will be very popular!一旦出版，这本词典将会非常畅销！Once he arrives we can start.他一到我们就可以动身。n.一次Do it just this once.只做这一次。For once he was telling the truth.他只有这一次说了实话。If one once loses self-confidence, he can never expect to be successful.一个人一旦失去了自信心,就甭想获得成功。Will once be enough?一次就够了吗?习惯用语all at once突然, 忽然at once马上，立刻；同时Do it at once.马上做。Dont all speak at once!大家别一块儿说话！once (and) for all最后一次Once and for all, we cant agree!最后再说一遍,我们不能同意!once or twice几次；一两次once upon a time从前Once upon a time there