1、When while as区别一、根据从句动作的持续性来区分1、“主短从长”型：即主句是一个短暂性动作，而从句是一个持续性动作，此时三者都可用。如：Jimhurthisarmwhilewhen，ashewasplayingtennis.吉姆打网球时把手臂扭伤了。2、“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，且强调主句动作或状态延续到从句所指的整个时间，此时通常要用while。IalwayslistentotheradiowhileImdriving.我总是一边开车一边听收音机。Hedidntaskmein;hekeptmestandingatthedoorwhilehere
2、adthemessage.他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边一边”之意时，则习惯上要用as。如：Heswunghisarmsashewalked.他走路时摆动着手臂。3、“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用as或when，但不能用while。如：Itwasraininghardwhenaswearrived.我们到达时正下着大雨。二、根据主句与从句动作是否同时发生来区分1、若主句与从句表示的是两个同时发生的短暂性动作，含有类似汉语“一就”的意思，英语一般要用as(也可用when)。如：
3、TheicecrackedaswhenIsteppedontoit.我一踩冰就裂了。2、若主句与从句表示的是两个几乎同时发生的短暂性动作，含有类似汉语“刚要就”“正要却”的意思，英语一般要用as(也可用when)，且此时通常连用副词just。如：Icaughthimjustwhenashewasleavingthebuilding.他正要离开大楼的时候，我把他截住了。三、根据是否具有伴随变化来区分若要表示主句动作伴随从句动作同时发展变化，有类似汉语“随着”的意思，英语习惯上要用as，而不用when或while。如：Theroomgrewcolderasthefireburntdown.随着炉火
4、逐渐减弱，房间越来越冷。注：若不是引导从句，而是引出一个短语，则用with，不用as。如：Withwintercomingon,itstimetobuywarmclothes.随着冬天到来，该买暖和衣裳了。四、根据从句动作的规律性来区分若暗示一种规律性，表示“每当的时候”，英语一般要用when。如：Itscoldwhenitsnows.下雪时天冷。五、根据主从句动作的先后顺序来区分若主句与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。如：Whenhearriveshelltellusallaboutthematch.等他到了，他会好好给我们讲讲那场比赛的情况。六、根据是否具
5、有“趁机”意味来区分1、若从句所表示的“当的时候”具有“趁机”的意味，则通常用while。如：Strikewhiletheironishot.趁热打铁。七、根据是否用作并列连词来区分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。如：IwasjustabouttogotobedwhenIheardaknockonthedoor.我正要睡觉，听见有人敲门。Onepersonmayliketospendhisvacationattheseashore,whileanothermaypreferthemountains.
6、八、根据所引出的省略句来区分1、as和when之后均可直接跟一个名词，构成省略句；但是while一般不这样用。如：AsWhenaboy,helivedinJapan.他小时候在日本。2、when和while之后可接现在分词、介词短语、形容词等构成省略句，但as一般不这样用。如：WhenWhilereading,hefellasleep.他看书时睡着了。一用所给动词正确行使填空1. I _ (have) my breakfast at half past six yesterday morning.2. Mary _ (go) over her lessons from six to seven
7、 last night. John and peter _(do) the same thing.3. What _ you _ (do) at that time? We _ (watch) TV.4. Was your father at home yesterday evening? Yes ,he was. He _ (listen) to the radio.5. They _(not make) a model ship when I saw him.6. _ they _ (have) a meeting at 4 yesterday afternoon?No, they _.
8、They _ (clean) the classroom.7. _ it _(rain) when you left school? Yes, it _. (No, it _)8. What _ your father _ (do) when he was your age?9. One day, Edison _ (wait) for a train to arrive, and suddenly a little boy ran to the track(轨道) to play.10. He asked me if I _ (go) fishing that afternoon.11. T
9、he three of them were in a hurry because their plane _ (leave) in five minutes.12. In a letter, john told us that he _ (come) to china next month.13. When the bell rang, jenny _ (wait) in her seat.14. She _ (make) her dress the whole afternoon.15. While my father _ (look) through the evening paper,
10、he suddenly _ a cry.16. When I _ (come) in the room, he _ (see) me, for he _ (read) something17. When we _ (arrive) at the village, it _ (get) dark and it _ (rain) hard.18. I _ (know) you _(wait) for me here.19. One day a little monkey _ (play) in a tall tree. A mother crocodile(鳄鱼) _ (look) for foo
11、d near the bank.20. What _ your father _ (do) yesterday evening? He _ (study) at the evening school.21. Later his parents found that he _ (sit) on some eggs.22. When he knocked at the door, my aunt _ (cook)23. The students _ (sing) and _ (dance) happily on the playground at that time.24. I _ (write)
12、 a letter when the door bell rang.25. We had no classed at that time. We _ (plant) trees.二.改错1.SheisfatbutIamthin.2.Itwasrainingwhilewearrived.3.Shesangwhilehewalked.三.选择最佳答案：1.ShethoughtIwaspraisingherchild，_，infact，Iwasscoldinghimforhisbadbehaviorsatschool.A.whatB.whileC.sothatD.therefore2.Idoever
13、ysinglebitofhousework_myhusbandBobjustdoesthedishesnowandthen.A.whileB.sinceC.whenD.as3.Wewereswimminginthelake_suddenlythestormstarted.A.whenB.whileC.untilD.befor四填空：when while1._Margowastalkingonthephone,hersisterwalkedin.2._wevisitedtheschool,thechildrenwereplayinggames.3._Sarahwasatthebarbers,Iw
14、asgoingtoclass.4._IsawCarlos,hewaswearingagreenshirt.5._Allenwascleaninghisroom,thephonerang.6._Ritaboughthernewdog,itwaswearingalittlecoat.7.Hewasdrivingalong_suddenlyawomanappeared.8._Jakewaswaitingatthedoor,anoldwomancalledtohim.9.Hewasreadingabook_suddenlythetelephonerang.10._itbegantorain,theyw
15、ereplayingchess.11.Shesawataxicoming_thewomanwaswaitingunderthestreetlight.12._theallienwasinthemuseum,Icalledthepolice.13.Theboywaswalkingdownthestreet_aUFOlanded.14._thealienwasvisitingthemuseum,theboycalledtheTVstation.15.Iwascleaningmyroom_thefirebrokeout.16._Lindashoutedhisname,somepeoplelookedather.
