外语屋教育
初中英语词汇精讲：when, while, as的用法
三者可表示“当…时候”，区别如下：
1. 若主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用：
He fell asleep when [while, as] he was reading. 他看书时睡着了。
【注】as 用于引出一个持续性动词表示“在…期间”时，其谓语通常不能是那些不用于进行时态的动词(如be, seem, love, want, agree, see, know, have 等)，所以下面一句中的while 不能换为as：
A：I’m going to the post office. 我要去邮局。
B：While you’re there, can you get me some stamps? 当你在邮局时，能帮我买几张邮票吗?
2. 若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while：
I kept silent while he was writing. 在他写的时候，我默不作声。
但是，若主从句表示的两个同时进行的动作含有“一边…一边…”之意思，通常用as：
She sang as she went along. 她边走边唱。
3. 若从句是一个短暂性动作，主句是一个持续性动作，可用as / when 但不用while：
It was raining hard when [as] we arrived. 我们到达时正下着大雨。
4. 若主从句表示的是两个同时(或几乎同时)发生的短暂性动作，用as / when：
I thought of it just when [as] you opened your mouth. 就在你要说的时候，我也想到了。
5. 若要表示两个正在发展变化的情况，相当于汉语的“随着”，一般用as：
Things are getting better and better as time goes on. 随着时间的推移，情况越来越好。
As it grew darker, it became colder. 天色越晚，天气越冷。
6. 表示“每当…的时候”(暗示一种规律性)，一般要用when：
It’s cold when it snows. 下雪时天冷。
He smiles when you praise him. 你夸奖他时他总是笑笑。
7. 若主从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when：
I will go home when he comes back. 他回来时，我就回家去。
8. when 可用作并列连词，表示“这时(突然)”；while 也可以用作并列连词，表示“而”、“却”(表示对比)；但as 则没有类似用法：
We were about to start when it began to rain. 我们正要出发，这时天开始下雨了。
He likes coffee, while she likes tea. 他喜欢咖啡，而她却喜欢茶。
爱心用心专心 1
Summary 3 Past Co nti nuous Tense 过去进行时总结 I. Defin itio n 时态含义 表示过去某一时刻或过去一段时间内正在进行的动作。 II. Time words 时间标志词 1. then, at that time, this time yesterday, at 6 o ' clock yesterday ... 2. when/ while/ (just) as 引导的时间状语从句 III. Structure 动词结构 was/ were + doing ? Whe n/ while/ (just) as 引导的时间状语从句在过去进行时态中的用法区别 1. when既可以和短暂性动词连用，也可以和连续性动词连用, 句中一般翻译为“当...... 时候” / “就在那时”。 a. Some one kno cked at the door whenI was hav ing breakfast. b. I was tak ing a bath whenthe teleph one rang. 2. while只可以和连续性动词连用 句中一般翻译成“当...... 时候”(=wheri) / “然而”(强调前后两个动作同时进行) a. He cut himself while he was shaving. b. My wife was cooking the dinner while I was working in the garden. 3. (just) as 更强调“随着”，所引导的从句动作一般与主句动作伴随着发生。 a. Just as I was ope ning the front door, the teleph one rang. b. The children were singing as they went home.
Unit 1 When were you born? 1.swimmer(swim, swam ,swum swimming)游泳者，游泳运动员 Ye Shiwen is a well-known s_________. 2.born( bear, bore, born) be born出生，出世 He was b_______in 1999./ He was b_____ in May 1999./ He was b____ on May Day, 1999. 3.ice (icy) 冰 He stood in the box of i______ for two days ,fifteen hours and forty-two minutes. 4.tower 塔 He stood on the t______ for one day and eleven hours. 5.admire 欣赏，仰慕guy 家伙，男人，小伙子 I a_________ that g________with great talent. 6.paint (painting) 用颜料画 He p________ pictures on the ground or on buildings. When did he started p____these pictures? 7.flat 水平的，平坦的 The pictures are f_________, but they look like they are 3D. 8.get in trouble 遇到麻烦 He sometimes got in t________for p_______the buildings at school. 9.Nobel Prize 诺贝尔奖literature 文学 Chinese writer Mo Yan has won the 2012 N______ P_______in L_______! Mo Yan won the N______ P_____ in L_____ in 2012. 10.as 因为，由于 Mo said he never expected to win the prize , a___ there were so many good writers all over the world. 11.drop out of school 辍学 When he was 12 (At the age of 12/, he d_______ o____ o___ school and started to work, first in his village and later in a factory. 12.means 方式，方法，途径try every means to do辍学 He had to try every m_______to find books to read. 13.at hand（时间或空间上）接近的，不远的 With no books at h_______, he started reading a Chinese dictionary. 14.publish 出版 His first short story was p______ in 1981. 15.novel 小说sorghum高粱director导演 He became famous in 1987 when his n______ Red S______was made into a film by the famous d______ Zhang Yimou. 16.frog 蛙 He also won the 18th Mao Dun Literature Prize in 2011 for his novel f_______. 17.works 作品，著作 More and more people are becoming interested in his w_______. 18.besides (except)除----之外 What other prize in literature did Mo Y an win b_______ the Nobel Prize. 19.perform(performance, performer) 表演，演出opera 戏剧 Mei Lanfang first f_______Beijing O________at the age of ten. 20.Brazilian 巴西的，巴西人national(nation, international,) 国家的，民族的 Ronaldo , the great B_________soccer player , played for his first n________team when he was 17 years old.
when 和while的用法区别 两者的区别如下： ①when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。 ②when 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。 ③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. ④when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。 一。引导时间状语从句时，WHILE连接的是时间段，而WHEN连接的多是时间点 例如What does your father do while your mother is cooking? What does your mother do when you come back? 二，WHILE可以连接两个并列的句子，而WHEN不可以 例如I was trying my best to finish my work while my sister was whtching TV 三，WHEN是特殊疑问词，对时间进行提问，WHILE不是。 例如，When were you bron? 续性动词和短暂性动词 英语中的动词，是学习中的重点，又是难点。英语中的动词有多种分类法。根据其有无含义，动词可分为实义动词和助动词；根据动词所表示的是动作还是状态，可以分为行为动词和状态动词；根据动词所表示的动作能否延缓，分为延续性动词和终止性动词。 可以表示持续的行为或状态的动词，叫做“延续性动词”，也叫“持续性动词”，如：be, keep, have, like, study, live, etc. 有的表示短暂、瞬间性的动词，叫做“终止性动词”，也可叫“短暂性动词”，或“瞬间性动词”，如die, join, leave, become, return, reach, etc.
when和while用法区别专项练习 讲解三例句： 1. The girls are dancing while the boys are singing. 2. Kangkang’s mother is cooking when he gets home. 3. When/While Kangkang’s mother is cooking, he gets home. 一、用when或者while填空 Margo was talking on the phone, her sister walked in. we visited the school, the children were playing games. · Sarah was at the barber’s, I was going to class. I saw Carlos, he was wearing a green shirt. Allen was cleaning his room, the phone rang. Rita bought her new dog; it was wearing a little coat. 7. He was driving along ________ suddenly a woman appeared. 8. _____ Jake was waiting at the door, an old woman called to him. 9. He was reading a book ______suddenly the telephone rang. 10. ______ it began to rain, they were playing chess. [ 二、用所给动词适当形式填空 11. While Jake __________ (look) for customers, he _______ (see) a woman. 12. They __________ (play) football on the playground when it _____ (begin) to rain. 13. A strange box ________ (arrive) while we _________ (talk). 14. John ____________ (sleep) when someone __________ (steal) his car. 15. Father still (sleep) when I (get) up yesterday morning. 16. Grandma (cook) breakfast while I (wash) my face this morning. 17. Mother (sweep) the floor when I (leave) home. ~ 18. I (read) a history book when someone (knock ) at the door. 19. Mary and Alice are busy (do) their homework. 20. The teacher asked us (keep) the windows closed. 21. I followed it (see) where it was going. 22. The students (play) basketball on the playground from 3 to 4 yesterday afternoon. / 三、完成下面句子，词数不限 1.飞机在伦敦起飞时正在下雨。 It when the plane in London. 2.你记得汶川大地震时你在做什么吗 Do you remember what you when Wenchuan Earthquake . 3.当铃声想起的时候，我们正在操场上玩得很开心。 We on the playground when the bell . 4.当妈妈下班回家时，你在做什么 % when Mum from work 5.当我在做作业时，有人敲门。 I was doing my homework, someone
when和while的用法解析、练习题及答案（附总结表格） 一、讲解三例句: 1. The girls are dancing while the boys are singing. 2. Lucy’s mother is cooking when she gets home. 3. When/While Lucy’s mother is cooking, she gets home. 二、用when或者while填空 1.______ Margo was talking on the phone, her sister walked in. 2.______ we visited the school, the children were playing games. 3.______ Sarah was at the barber’s, I was going to class. 4.______ I saw Carlos, he was wearing a green shirt. 5.______ Allen was cleaning his room, the phone rang. 6.______ Rita bought her new dog; it was wearing a little coat. 7. He was driving along ________ suddenly a woman appeared. 8. _____ Jake was waiting at the door, an old woman called to him. 9. ______ it began to rain, they were playing chess. 10. She saw a taxi coming ______ the woman was waiting under the streetlight. 三、语法 while和when都是表示同时，到底句子中是用when还是while主要看主句和 从句中所使用 的动词是短暂性动作(瞬时动词)还是持续性动作。 1、若主句表示一个短暂性动作，而从句表示的是一个持续性动作时，用 When/While。如: He fell asleep when while he was reading. 他看书时睡着了。
WHEN与WHILE用法区别 when, while这三个词都有"当……时候"之意，但用法有所不同，使用时要特别注意。 ①when意为"在……时刻或时期"，它可兼指"时间点"与"时间段"，所引导的从句的动词既可以是终止性动词，也可是持续性动词。如： When I got home, he was having supper.我到家时，他正在吃饭。 When I was young, I liked dancing.我年轻时喜欢跳舞。 ②while只指"时间段"，不指"时间点"，从句的动词只限于持续性动词。如：While I slept, a thief broke in.在我睡觉时,盗贼闯了进来。 辨析 ①when从句与主句动作先后发生时，不能与while互换。如： When he has finished his work, he takes a short rest.每当他做完工作后，总要稍稍休息一下。(when = after) When I got to the cinema, the film had already begun.当我到电影院时，电影已经开始了。(when=before) ②when从句动词为终止性动词时，不能由while替换。如： When he came yesterday, we were playing basketball.昨天他来时，我们正在打篮球。 ③当从句的谓语是表动作的延续性动词时，when, while才有可能互相替代。如：While / When we were still laughing, the teacher came in.正当我们仍在大声嬉笑时，老师进来了。 ④当从句的谓语动词是终止性动词，而且主句的谓语动词也是终止性动词 时,when可和as通用，而且用as比用when在时间上更为紧凑，有"正当这时"的含义。如： He came just as (or when) I reached the door.我刚到门那儿，他就来了。 ⑤从句的谓语动词如表示状态时，通常用while。如： We must strike while the iron is hot.我们应该趁热打铁。 ⑥while和when都可以用作并列连词。
as when while 的区别和用法 as when while的用法 一、as的意思是“正当……时候”,它既可表示一个具体的时间点，也可以表示一段时间。as可表示主句和从句的动作同时发生或同时持续，即“点点重合”“线线重合”；又可表示一个动作发生在另一个动作的持续过程中，即“点线重合”， 但不能表示两个动作一前一后发生。如果主句和从句的谓语动词都表示持续性的动作，二者均可用进行时，也可以一个用进行时，一个用一般时或者都用一般时。 1、As I got on the bus，he got off. 我上车，他下车。（点点重合）两个动作都是非延续性的 2、He was writing as I was reading. 我看书时，他在写字。（线线重合）两个动作都是延续性的 3、The students were talking as the teacher came in. 老师进来时，学生们正在讲话。（点线重合）前一个动作是延续性的，而后一个动作时非延续性的 二、while的意思是“在……同时（at the same time that )”“在……期间(for as long as, during the time that）”。从while的本身词义来看，它只能表示一段时间，不能表示具体的时间点。在时间上可以是“线线重合”或“点线重合”，但不能表示“点点重合”。例如： 1、He was watching TV while she was cooking. 她做饭时，他在看电视。（线线重合） 2、He was waiting for me while I was working. 我工作的时候，他正等着我。（线线重合） 3、He asked me a question while I was speaking. 我在讲话时，他问了我一个问题。（点线重合）
过去进行时过去进行时表示过去某一时刻或者某段时间正在进行或发生的动作，常和表过去的时间状语连用，如： 1. I was doing my homework at this time yesterday. 昨天的这个时候我正在做作业。 2. They were waiting for you yesterday. 他们昨天一直在等你。 3. He was cooking in the kitchen at 12 o'clock yesterday. 昨天12点，他正在厨房烧饭。 过去进行时的构成： 肯定形式：主语+was/were+V-ing 否定形式：主语+was not (wasn't)/were not (weren't)+V-ing 疑问形式：Was/Were+主语+V-ing。 基本用法： 1. 过去进行时表示过去某一段时间或某一时刻正在进行的动作。常与之连用的时间状语有，at that time/moment, (at) this time yesterday (last night/Sunday/week…), at+点钟+yesterday (last night / Sunday…)，when sb. did sth.等时间状语从句，如： 1）What were you doing at 7p.m. yesterday? 昨天晚上七点你在干什么？ 2）I first met Mary three years ago. She was working at a radio shop at the time. 我第一次遇到玛丽是在三年前，当时她在一家无线电商店工作。 3）I was cooking when she knocked at the door. 她敲门时我正在做饭。 2. when后通常用表示暂短性动词，while后通常用表示持续性动词，而while所引导的状语从句中，谓语动词常用进行时态，如： When the car exploded I was walking past it. = While I was walking past the car it exploded. 3. when用作并列连词时，主句常用进行时态，从句则用一般过去时，表示主句动作发生的过程中，另一个意想不到的动作发生了。如： I was walking in the street when someone called me. 我正在街上走时突然有人喊我。 4. when作并列连词，表示“（这时）突然”之意时，第一个并列分句用过去进行时，when引导的并列分句用一般过去时。如：
When和while在初中英语学习中的要点归纳when 既可用作副词，又可用作连词，也可用作代词。由于when 的用法是既是学生学习的重点难点，又是中考考试考查的热点之一。下面就when 的用法作如下归纳： 一、用作疑问副词，意思为“什么时候、何时”，引导特殊疑问句或后跟动词不定式。例如： When will you come to see me? 你什么时候要来看我？ When are they going to visit the Great Wall? 他们打算什么时候去游览长城？ I don't know when to leave for London. 我不知道该在何时动身去伦敦。 二、when 用作连词，意为“当……的时候”，引导时间状语从句。 When 在引导时间状语从句时，主从复合句的时态相互制约，要保持主从复合句时态的大体一致。也就是说，要么都是现在时态，要么就是过去时态。现在时态包括：一般现在是、一般将来时、现在进行时以及现在完成时；过去时态包括：一般过去时、过去进行时、过去将来时和过去完成时。when在构成时间状语从句时，主要有以下特点： 1.when后面所跟的句子不可能运用现在进行时、过去进行时、现在完成时、过去完成时、一般将来时以及过去将来时。 2.主句+ when +从句，时态制约如下： （1）主句用一般将来时，从句用一般现在时，如： Jim will ring you up when he comes back. 当吉姆回来的时候，他将给你打电话。 （2）主句用情态动词原形，从句用一般现在时，如： She can help me with my English when she has time. 当她有空的时候，他能帮助我学习英语。 （3）主句是祈使句，从句用一般现在时，如： Please leave here when I begin working.当我开始工作的时候，请离开这儿。 （4）主句用一般过去时，从句用一般过去时，如： They learned a lot from the peasants when they stayed in the village. 他们住在那个村子时，从农民那里学到了许多东西。 （5）主句用过去进行时，从句用一般过去时，如： It was snowing when he arrived at the station. 他到达车站时，天正下着雪。
when 和while的用法区别 ①when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。 ②when 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。 ③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. ④when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。 when，while，as引导时间状语从句的区别 when，while，as显然都可以引导时间状语从句，但用法区别非常大。 一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。 ①Why do you want a new job when youve got such a good one already？（get 为短暂性动词）你已经找到如此好的工作，为何还想再找新的？ ②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。 ③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。 ④The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。 二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while和as从句的谓语动作必须是和主句谓语动作同时发生。 1．从句动作在主句动作前发生，只用when。 ①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。 ②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。 2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。
When while as的区别和用法 when的用法 当主句使用持续性动词时. Dave was eating,when the doorbell rang.门铃响时,大卫在吃饭. 2.一个动作紧接着另一个动作发生. When the lights went out, I lit some candles.灯灭了,我赶紧点上一些蜡烛. 3.谈论生命中的某一阶段,或过去的某段时间. His mother called him Robbie when he was a baby. 在他很小时,他妈妈叫他Robbin. 4.指"每一次" When I turn on the TV, smoke comes out the back. 每当我打开电视,就有烟从后面冒出. while/as 的用法 从句多为进行时,而且为持续性动词. I'll look after the children while you are making dinner. 你做饭,我来照顾孩子. 注意事项: (1) “主短从长”型：主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用： He fell asleep when [while, as] he was reading. 他看书时睡着了。 Jim hurt his arm while［when，as］he was playing tennis. 吉姆打网球时把手臂扭伤了。 As［When，While］she was waiting for the train，she became very impatient. 她在等火车时，变得很不耐烦。 (2) “主长从长”型：若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while： Don’t talk while you’re eating. 吃饭时不要说话。 I kept silent while he was writing. 在他写的时候，我默不做声。 但是，若主从句表示的两个同时进行的动作含有“一边…一边”之意思，通常用as：
When + doing"的用法 Every teacher should, therefore, follow in his footsteps and emphasize benevolence when teaching. 因此，每个老师教学时，应效法孔子并强调仁的道理。 = Every teacher should,therefore,follow in his footsteps and emphasize benevolence when he teaches . 在以when,while,if, once ,though,unless 等六个连词引导的状语从句中，若主语与主句的主语相同时，可将从句中的主语删除，并将之后的动词变成现在分词。若是be动词，一律变成分词being,而being再予以省略。 1. when you do the work, you should be careful. = When doing the work, you should be careful. 2. If I am free, I'll do it. = If free, I'll do it. 3. when you do the work, you must be careful. = When doing the work, you must be careful. 4. Though he is poor, he is happy. = Though poor, he is happy. 5. While I was watching Tv, I fell asleep. = While watching TV. I fell asleep. 6. When you drive a car, you should be alert. = When driving a car, you should be alert.
when和while when和while都可表示“当……的时候”，引导时间状语从句。你知道两者在过去进行时中的用法有什么不同吗？ 请仔细观察下面的例句，然后补全空格中的内容。 ①I was walking to school when I saw a cat in a tree. ②When Sally arrived home, her mother was cleaning the house. 主句的动作是持续性的，而从句动作是短暂性的，此时用_______引导时间状语从句，主句用_____________时态，从句用一般过去时态。 ③While I was sleeping in the bedroom, someone knocked at the door. ④David fell while he was riding his bike. 主句的动作是短暂性的，从句的动作是持续性的，此时用_________引导从句，主句用____________时态，从句用过去进行时态。 ⑤While Andy was waiting for the bus, he was reading a newspaper. ⑥He was cleaning his car while I was cooking. 主句和从句的动作在过去的某时刻或某段时间同时发生，而且动作都是持续性的，此时用_________引导从句，而且主句和从句都用_____________ 时态。 练习：用when 和while 填空 1. We were singing __________ the teacher came in. 2. _________ I was doing my homework , my mother was cooking. 3. What were you doing _________ the rainstorm came ? 4. ________ I was waiting for the bus at the bus station, it began to rain. 5. ________ he woke up, the smoke was rising.
when 引导的从句用法一、引导时间状语从句 1. 表示"当……的时候",相当于at the moment when。例如: When we got to the cinema, the film had been on for half an hour. 当我们到达电影院时,电影已放映半小时了。She was writing a letter when I came in. 当我进来时,她在写信。 2. 表示"一……就……",相当于as soon as。例如: The students got up when the bell rang. 铃声一响,学生们就起床了。I'll ring you up when I arrive in Beijing. 我一到北京就给你打电话。 3. 表示"就在这时;当时",相当于just at the moment或just then .例如: We were about to start out when it began to rain heavily. 我们正要启程,就在这时,天下起了大雨。 He had just returned from one business trip when he was asked to make another one. 他刚刚出差回来,这时,又叫他再次出差。 4. 表示"每当;每次",相当于every time或whenever。例如: She always turns to us for help when she is in trouble.每当她遇到困难,她总是向我们求助。It is freezing cold here when it snows. 每当这儿下雪,天气就十分寒冷。 5. 表示"当……之后;在……以后",相当于after the time that。例如: We went home when the film was over. 电影结束以后,我们回家去了。When she got home, she started to prepare supper. 她回到家后,开始准备晚饭。 二、引导条件状语从句 when引导的条件状语从句相当于if/ in case引导的条件状语从句.例如: When there is no gravity, our feet can no longer stay on the ground. 如果没有重力,我们的脚就不能够在地面上站稳。Turn off the switch when anything goes wrong with the machine. 如果机器发生故障,就把电闸关上。 三、引导原因状语从句when引导原因状语从句时,相当于since/now that引导的原因状语从句。例如: How can they learn anything when they spend all their spare time watching television? 他们把所有的空闲时间都用来看电视了,还能学到什么东西呢? Why do you want a new job when you have got such a good one? 既然你已经有了这么好的一份工作,为什么还要再找新的工作呢? 四、引导让步状语从句when引导的让步状语从句相当于though或although引导的让步状语从句。例如: He usually walks when he might ride. 虽然有车可乘,但他通常是步行。 The little girl can tell right from wrong when she is only twelve. 这个小女孩虽然只有十二岁,却能分清是非。 五、引导定语从句when引导定语从句时,有时可用in which或on which来替代。例如:We'll put off the picnic until next week, when the weather may be better. 我们要把野餐推迟到下周,那时可能天气好些。 I'll never forget the day when I joined the Party. 我将永远不会忘记我入党的那一天。 六、引导名词性从句 1. 引导宾语从句。例如: Please tell us when his father will return from abroad. 请告诉我们他父亲什么时候从国外回来。 2. 引导主语从句。例如: When they will leave for Australia hasn't been decided. 他们什么时候动身去澳大利亚还没有决定。 3. 引导表语从句。例如: The question is when they will get so much money to set up the factory. 问题是他们将在什么时候弄到这么多钱来把这个工厂办起来。 when, while 和as 引导时间状语从句的用法 这三个词的意思很简单，都有“当……时候”的意思。但学生经常会问三个词的区别在哪儿，特别是在做选择题的时候。别说是学生，就我个人而言，做这样的选择题要保证百分之百的正确也是不可能的。现根据大量的实例和个人的思考，做一点小结，供大家参考。 一、when 的用法如果只从现象来看，when 从句用的最多的是一般过去时，而主句的时态没有限制,根据具体情况而定1. When he was a child he was always trying out new ideas. 他小时候就常常试验一些新的设想。 2. When she came into my room, I was just reading a book. 她走进我房间时，我正在看书。 3. Were you writing when the teacher came in? 老师进来的时候，你在写信吗？ 4. Sorry, I was out when you called me. 对不起，你打电话来的时候我出去了。 5. He was on the point of leaving when someone knocked at the door. 他正要走，这时有人敲门。 6. I thought of it just when you opened your mouth. 就在你要说话的时候，我也想到了。
when和while的用法和区别 while和when都是表示同时，到底句子中是用when还是while主要看从句和主句中所使用的动词是短暂性动作（瞬时动词）还是持续性动作。 1、若主句表示的是一个短暂性的动作，而从句表示的是一个持续性动作时，两者都可用。如：He fell asleep when [while] he was reading. 他看书时睡着了。 I met him when [while] I was taking a walk in the park. 我在公园散步时遇到了他。 2、若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while。如： Don’t talk while you’re eating. 吃饭时不要说话。 I kept silent while he was writing. 在他写的时候，我默不作声。 3、若从句是一个短暂性动作，而主句是一个持续性动作，可以when 但不用while。如：When he came in, I was listening to the radio. 他进来时，我在听收音机。 It was raining hard when we arrived. 我们到达时正下着大雨。 4、若主、从句表示的是两个同时(或几乎同时)发生的短暂性动作，一般要用when。如： I thought of it just when you opened your mouth. 就在你要说的时候，我也想到了。 至于什么是短暂性动作，什么是持续性动作，其实有个很简单的规律。就是如果是进行时态，一般是持续性的。如果是过去式，一般是短暂性动作。 对于，填写when还是while的问题，通常首先看主句和从句中的时态，再根据以上4个规律来判断填写那个单词。 When和While的区别 通常when 后面接一般过去时while 后面接过去进行时 ①when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。 ②when 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。 ③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. ④when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.