since+時(shí)間點(diǎn)
for+時(shí)間段
eg:He has kept the book for two weeks.
He borrowed the book since two weeks ago.
注意動(dòng)詞的時(shí)態(tài),for后面是一段時(shí)間,動(dòng)詞用完成式,而since后面是一個(gè)時(shí)間點(diǎn),動(dòng)詞用過(guò)去式.兩周前的一天,與for two weeks的兩個(gè)星期這樣14天相比是一個(gè)點(diǎn).
一、延續(xù)性動(dòng)詞
延續(xù)性動(dòng)詞表示的動(dòng)作不但可以延續(xù),而且可以產(chǎn)生持久的影響.常見(jiàn)的這類動(dòng)詞有：be,have,keep,know,learn,lie,live,read,sing,sleep,stand,stay,wait,walk,watch等.延續(xù)性動(dòng)詞的用法很廣,但常見(jiàn)于現(xiàn)在完成時(shí)中的句子中,且常與for,how,long,since等引導(dǎo)的表示一段時(shí)間的狀語(yǔ)或狀語(yǔ)從句連用.例如：
1．I have learned more than 1,000 Chinese words since I came to China．
自從來(lái)到中國(guó),我已經(jīng)學(xué)會(huì)了l,000多個(gè)漢字.
2．We have lived in Linqing since we came here．自從來(lái)到這兒,我們就一直住在臨清.
3．I have kept the picture for about three years．這張畫(huà)我保存了大約三年.
二、終止性動(dòng)詞
終止性動(dòng)詞又稱為瞬間動(dòng)詞或非延續(xù)性動(dòng)詞,它表示的動(dòng)作不能延續(xù),也就是說(shuō)動(dòng)作一旦發(fā)生就立即結(jié)束,并產(chǎn)生某種結(jié)果.常見(jiàn)的這類動(dòng)詞有：accept,arrive,become,begin,borrow,break,buy,catch,close,come,die,end,fall,finish,get,give,go,join,leave,put,reach,receive,shut,start,stop等.終止性動(dòng)詞用在現(xiàn)在完成時(shí)要注意下面三點(diǎn)：
（一）終止性動(dòng)詞可直接用來(lái)表示某一動(dòng)作的完成.例如：
1．They have reached Shanghai．他們已經(jīng)到達(dá)了上海.
2．Has he gone to London?他已經(jīng)到倫敦去了嗎?
（二）終止性動(dòng)詞表示的動(dòng)作極其短暫,不能持續(xù),所以,在現(xiàn)在完成時(shí)中一般不能和以since,for等引導(dǎo)的表示一段時(shí)間的狀語(yǔ)連用.例如：
1．那老人已經(jīng)死了一周了.The old man has died for a week．(誤)
2．他三天前就已經(jīng)來(lái)這兒了.He has come here since three days ago．(誤)
在以上兩句中,die和come都是終止性動(dòng)詞,可用于現(xiàn)在完成時(shí),但不能與以
since或for引導(dǎo)的表示一段時(shí)間的狀語(yǔ)連用.那么,上面兩個(gè)句子應(yīng)該怎樣譯成英語(yǔ)呢?請(qǐng)看下面四種譯法：
1．把終止性動(dòng)詞改為延續(xù)性的動(dòng)詞.例如：
①The old man has been dead for a week．
②He has been here since three days ago．
2．把原句中的一段時(shí)間改為表示“過(guò)去”的時(shí)間,時(shí)態(tài)由現(xiàn)在完成時(shí)改變成一般過(guò)去時(shí).例如：
①The old man died a week ago．
②He came here three days ago．
3．用“It is+時(shí)間+since…”句式.例如：
①I(mǎi)t is／has been a week since the old man died．
②It has been／is three days since he came here．
4．用“多長(zhǎng)時(shí)間+has passed+since…”句式.例如：
①A week has passed since the old men died．
②Three days had passed since he came here．
(三)有關(guān)特殊終止性動(dòng)詞的用法.
1．在while(表示一段時(shí)間)引導(dǎo)的從句里,謂語(yǔ)動(dòng)詞不能使用終止性動(dòng)詞,但可以把while改成when,這樣,從句里的謂語(yǔ)動(dòng)詞就可以使用終止性動(dòng)詞了.因?yàn)閣hen既可以表示時(shí)間的“點(diǎn)”,又可以表示時(shí)間的“段”.例如：
While he got to America．he found his English Was very poor．(誤)
When he got t0 America．he found his English was very poor．(正)
2．終止性動(dòng)詞的否定式與until連用時(shí),意為“直到……才／不到什么時(shí)間不……”等.例如：
Don’t get off until the bus stops．車未停穩(wěn),切勿下車.
3．終止性動(dòng)詞不可以與how long引導(dǎo)的句式連用.例如：
How long have you borrowed the magazine?(誤)
When did you borrow the magazine?(正)
How long have you kept the magazine?(正)