短暂性动词,延续性动词和现在完成时短暂性动词是指动作一旦发生就立即结束.它不能和一段时间连用.这类动词有：go,come,arrive,leave,begin,start,join,marry等；短暂性动词的肯定式不能与表示一段时间的for或since或howlong等状语连用.例如：Hisfathergotill.Ihavereceivedhisletter.但是,不可以说：Hisfathergotillforaweek.Ihavereceivedhisletterforthreedays.在否定句中,短暂性动词可以和表示一段时间的状语连用.例如：Wehaven’theardfromJaneforalongtime.Isupposesomethingmusthavehappenedtoher.延续性动词是指动作发生后还可以延续一段时间或者相当长的一段时间.如：live,work,study,learn,sleep等,延续性动词可以和表示一段的时间状语连用.值得注意的是,表示一段时间的状语除了“for+一段时间”外,还有since+n./从句（时间点）,since+时间段+ago,疑问词howlong,inthepast+时间段,allthese+时间段,from…to（时间点）以及till/until+n./句子等等.例如：Howlong_______yourbrotherjoinedthearmy?A.hasB.hadC.isitsinceD.wastherethat通过审题,答案B和D很容易被排除,但是稍不注意便会选中答案A；殊不知howlong为一段时间的状语,不能与非延续性动词短语hasjoined连用,所以这题的正确答案是C.另外,动词的延续性与非延续性还体现在这两种句型中：延续性动词的肯定式+till/until短暂性动词的否定式+till/until请看例句：Wewaiteduntilhecame.Ididn’tgotobeduntilmyfathercamebackhomelastnight.如果短暂性动词与表示一段时间的时间状语连用,必须将短暂性动词改为延续性动词.现归纳总结一下由非延续性动词到延续性动词的转换：arrive→beherebegin(start)→beondie→bedeadcomeback→bebackleave→beaway(from)fallill(sick,asleep)→beill(sick,asleep)getup→beupgoout→beoutfinish→beoverputon→wear或beonopen→beopenjoin→bein或beamemberof…close→beclosedgotoschool→beastudentborrow→keepbuy/get→havecatch(acold)→have(acold)gettoknow→knowbegintostudy→studycometowork→workmoveto→liveinfinish/end→beovercometo→beinsitdown→beseatedmarry→bemarrieddress→bedressed等如：Hehasbeenasoldierforthreeyears.他参军三年了.Hisfatherhasbeendeadfortwoyears.他父亲去世二年了.Thefilmhasbeenonfortenminutes.电影已开始十分钟了.WehavestudiedEnglishforthreeyears.我们（开始）学英语已三年了.HowlongcanIkeepthisbook?这本书我可以借多长时间?除了用上面的转化形式之外,还可以用其他的表达形式：A.Itis/hasbeen+时间+since……（动词用过去式）,B.主语+谓语（过去时）+时间+ago.例如：It’sfivedayssinceIreceivedhisletter.Hisfatherdiedthreeyearsago.看一个句子可以用以下几种说法：他离开上海已经3天了.HeleftShanghaithreedaysago.HehasbeenawayfromShanghaiforthreedays.HehasbeenawayfromShanghaisincethreedaysago.Itis/hasbeenthreedayssinceheleftShanghai.ThreedayshaspassedsinceheleftShanghai.