英语中,动词按其动作发生的方式、动作发生过程的长短,可分为延续性动词和短暂性动词.
延续性动词表示能够延续的动作,这种动作可以延续下去或产生持久影响.如：stay, live, learn, study, work, wait, watch, sing, read等.
短暂性动词也称非延续性动词、瞬间动词,表示不能延续的动作,这种动作发生后立即结束.如open, close, finish, begin, come, go, arrive, reach, get to, leave, move, borrow, buy, die等.
现在完成时常跟表示一段时间的时间状语,如“for +一段时间”、“since +时间点”、“during the past+一段时间 ”等,因此谓语必须是一种状态或表示延续性的动作,具体来说,它必须是延续性动词及其短语、短暂性动词及其短语的否定式,或表示状态的词或短语.
常用的短暂性动词与延续性动词的转换
buy---have get up---be up borrow---keep
leave---be away from put on---be on
go to town---be in town lose---be missing
catch a cold---have a cold close---be not open
open(v.)---be open(adj.) fall ill---be ill
close---be not open come back---be back
join---be in /be a member
come to/arrive at(in)/reach/get to---be here/there
begin/start to learn/study/work/teach --- learn/study/work/teach
一、延续性动词和终止性动词的概念
英语中,动词按其动作发生的方式、动作发生过程的长短,可分为延续性动词和终止性动词.
延续性动词表示能够延续的动作,这种动作可以延续下去或产生持久影响.如：learn, work, stand, lie, know, walk, keep, have, wait, watch, sing, read, sleep, live, stay等.
终止性动词也称非延续性动词、瞬间动词或短暂性动词,表示不能延续的动作,这种动作发生后立即结束.如open, close, finish, begin, come, go, arrive, reach, get to, leave, move, borrow,buy等.
二、延续性动词的用法特征
1.延续性动词可以用于现在完成时,其完成时态可与表示"段时间"的状语连用.表示"段时间"的短语有：for two years, during the past three years, since last year, how long等.如：I have learned English since I came here.自从我来到这儿就学英语了.
2.延续性动词不能与表示短暂时间的"点时间"状语连用.如：It raind at eight yesterday morning.(误) rain为延续性动词,而at eight表示"点时间",前后显然矛盾.如果用延续性动词表示一瞬间的动作,可以借助come, begin, get等终止性动词来表示.上句可改为：It began to rain at eight yesterday morning.(正)又如：
-When did you get to know Jack?
-Two years ago.
-Then you've known each other for more than two years.
-That's right.
三、终止性动词的用法特征
1.终止性动词可用来表示某一动作完成,因此可用于现在完成时.如：
The train has arrived.火车到了.
Have you joined the computer group?你加入电脑小组了吗?
2.终止性动词表示的动作极其短暂,不能持续.因此,不可与表示一段时间的状语连用(只限肯定式).如：
(1)他死了三年了.
误：He has died for three years.
正：He has been dead for three years.
正：He died three years ago.
正：It is three years since he died.
正：Three years has passed since he died.
(2)他来这儿五天了.
误：He has come here for five days.
正：He has been here for five days.
正：He came here five days ago.
正：It is five days since he came here.
正：Five days has passed since he came here.
(1)、(2)句中的die、come为终止性动词,不能与表示"段时间"的状语连用.那么,应如何正确表达呢?可以采用下面的四种方法：
(1)将句中终止性动词转换为相应的延续性动词,如上面两例中的第一种正确表达方式.下面列举几例：leave→be away, borrow→keep, buy→have, begin/start→be on, die→be dead, move to→live in, finish→be over, join→be in/be a member of, open sth.→keep sth. open, fall ill→be ill, get up→be up, catch a cold→have a cold.
(2)将句中表示"段时间"的状语改为表示过去确定时间的状语,如下面两例中的第二种正确表达方式.
(3)用句型"It is+段时间+since..."表达原意,如上面两例中的第三种正确表达方式.
(4)用句型"时间+has passed+since..."表达原意,如上面两例中的第四种正确表达方式.
3.终止性动词可用于现在完成时否定式中,成为可以延续的状态,因而可与表示一段时间的状语连用.如：
He hasn't left here since 1986.
I haven't heard from my father for two weeks.
4.终止性动词的否定式与until/till连用,构成"not+终止性动词+until/till ..."的句型,意为"直到……才……".如：
You can't leave here until I arrive.直到我到了,你才能离开这里.
I will not go to bed until I finish drawing the picture tonight.今天晚上直到我画完画,我才上床睡觉.
5.终止性动词可以用于when引导的时间状语从句中,但不可以用于while引导的时间状语从句中.when表示的时间是"点时间"(从句谓语动词用终止性动词),也可以是"段时间"(从句谓语动词用延续性动词).而while表示的是一个较长的时间或过程,从句谓语动词用延续性动词.如：
When we reached London, it was twelve o'clock. (reach为终止性动词)
Please look after my daughter while/when we are away. (be away为延续性动词短语)
6.终止性动词完成时不可与how long连用(只限于肯定式).如：
误：How long have you come here?
正：How long have you been here?
正：When did you come here?