before和until的用法及区别.ppt

.,.,before与until,1.Myfriendswalkedmetothebusstopandwaitedwithme_thebusarrived.（before；until）,此题不能选before，因为时态不对。如果把walked和waited改成过去完成式hadwalked和hadwaited就可以选before。before的使用一般有强烈的时态要求而until一般没有时态要求,until,Iwaited_hecameback.我一直等到他回来。,Ididntleave_hecameback.直到他回来我才走,Icanonlygiveyouananswer_Ithinkitover.,until,until,before,untilbefore区别实际上，只要我们把握住两者使用时本身的含义及主句动词是终止性的，还是延续性的，肯定式，还是否定式两大点，就能容易地解决这类问题。现详细阐明如下：一、在下列情况下，两者可互换用，但含义略有不同。before表示“在之前”的意思，强调时间先后关系；而until表示“直到才”的意思，主句是肯定句则表示主句动作的终止时间；主句是否定句则强调主句动作的起始时间。,1.主句为否定式终止性谓语动词。常见的动词是open,start,leave,arrive,finish,stop等。例如：(1)Thenoiseofthestreetdidntstopuntil/beforeitwasmidnight.(2)Thechildrenwontcomebackuntil/beforeitisdark.(3)Ididntleavethelovelyboyuntil/beforehismothercamehome.,2.主句为肯定式、延续性谓语词，这类动词用stand,stay,talk,be,wait等。例如：(1)Helivedwithhisparentsuntil/beforehegraduatedfromschool.(2)Iwillwaituntil/beforehecomestomyhelp.(3)Ishallstayhereuntil/beforeyoucomeback.,二、在下列情况下，用before不用until。1.主句这肯定式、终止性谓语动词，只用before。例：(1)HefellasleepbeforeIcouldtakeoffhisclothes.(2)Wearrivedtherebeforeitstartedtorain.(3)TheholidaycametotheendbeforeIknewit.(4)Healmostknockedmedownbeforehesawme.,2.主句谓语动词强调动词的迟缓性，只用before，常伴有时间段状语或时间段暗示。例：(1)Itwasquitesometimebeforehefoundtheelephantatall.(2)Wehadwalkedalongwaybeforewefoundsomewater.(3)Wehadsailedfortwodaysbeforewesawtheland.(4)Thefirelastedaboutfourhoursbeforethefirefighterscouldcontrolit.,(5)Itwasmidnightbeforemybrothercamehome.(6)Itwasthreemonthsbeforetheymetagain.,3.如果强调从句谓语动作未发生，就发生主句谓语动作，只用before。常译为“未及”，“不”或“不等就”。例：(1)Wecanleaveearlyinthemorningbeforeitgetstoohot.(2)ImustwriteitdownbeforeIforgetit.(3)Wedowanttobuysomethingnowbeforepricesgoup.,4.表“与其说倒不如”，“与其毋宁”只用before。例：(1)IwouldgiveupmyjobbeforeIdagreetobedismissed.(2)Hewilldieofhungerbeforehewillsteal.,5.在某些特定句型中用before。例如：(1)Itwasnotlongbeforethewholecountryroseup.(2)Itwillprobablynotbelongbeforetheyunderstandeachother.,三、下列情况一般区别用until。1.主句是持续性谓语动词时，肯定、否定都可以，但意义完全不同。肯定表动作终止，而否定表动作开始。例如：(1)Wediscussedtheproblemuntil/beforehecameback.我们一直讨论到他回来。(2)Wedidntdiscusstheproblemuntilhecameback.我们一直等到他回来后才讨论问题。,2.notuntil句型尽管在某些情况下可与before互换用，但在强调句中一般仍用until。例如：(1)ItwasnotuntilhetoldmethatIknewit.(2)Itwasnotuntilhefinishedhishomeworkthathewenthome.,Theywereta