《大学英语语法》课程电子教案（PPT课件）02 完成时的用法、一般过去时与现在完成时的区别、时态的呼应

4)完成时的用法 A)Use of present perfective Present perfective,a combination of the perfective aspect with the present tense (have/has +-ed participle )has two chief uses:finished"use and "unfinished"use. The finished"use refers to the present result of a past event still operative at the present moment.The "unfinished"use of the present perfective denotes that an action or state extends over a period lasting up to the present moment,possibly extending into the future as well

1 4)完成时的用法 A) Use of present perfective Present perfective, a combination of the perfective aspect with the present tense (have / has + -ed participle ), has two chief uses: “finished” use and “unfinished” use. The “finished” use refers to the present result of a past event still operative at the present moment. The “unfinished” use of the present perfective denotes that an action or state extends over a period lasting up to the present moment, possibly extending into the future as well

The difference between these two uses manifests itself in the fact that in the unfinished"use,the present perfective is commonly accompanied by an adverbial expressing duration,but no such ac- companying adverbial is present in the "finished"use.Compare: 号He's turned off the light.(灯在一个过去时间被关掉， 说话时仍然关着。) He's lived here since1960.(他从1960年来到这里居 住，至今还住在这里，偶尔也可根据上下文理解为刚刚 搬走。) B)Uses of past perfective The past perfective (had +-ed participle)also 2

2 The difference between these two uses manifests itself in the fact that in the “unfinished” use, the present perfective is commonly accompanied by an adverbial expressing duration, but no such ac￾companying adverbial is present in the “finished” use. Compare: He’s turned off the light. （灯在一个过去时间被关掉， 说话时仍然关着。） He’s lived here since 1960. （他从1960年来到这里居 住，至今还住在这里，偶尔也可根据上下文理解为刚刚 搬走。） B) Uses of past perfective The past perfective (had + -ed participle) also

has two chief uses:"finished"use and "unfinished"use,only with time reference back-shifted to a specified past moment. In the finished"use the past perfective denotes an action or state already in completion before a specified past,and in its unfinished"use,it denotes an action or state extending over a period up to a past moment and possibly into the future in the past,eg: &I had written the article when he came.(已经写完了 文章) By six o'clock they had worked twelve hours..(他们可 能还会继续工作下去)

3 has two chief uses: “finished” use and “unfinished” use, only with time reference back-shifted to a specified past moment. In the “finished” use the past perfective denotes an action or state already in completion before a specified past, and in its “unfinished” use, it denotes an action or state extending over a period up to a past moment and possibly into the future in the past, eg: I had written the article when he came. (已经写完了 文章) By six o’clock they had worked twelve hours. (他们可 能还会继续工作下去)

Note:Past perfective in sentences with when-/before-/after-/ until-clauses Subordinators such as when,before,after unti/can sometimes be used interchangeably when they connect clauses where two actions happen one after another.The general rule is that the earlier happening is expressed by the past perfective and the later happening by the simple past.Compare: When I reached the station,the train had already left. I reached the station after the train had left. I didn't reach the station unti/after the train had left

4 Note: Past perfective in sentences with when-/ before-/ after-/ until- clauses Subordinators such as when, before, after, until can sometimes be used interchangeably when they connect clauses where two actions happen one after another. The general rule is that the earlier happening is expressed by the past perfective and the later happening by the simple past. Compare: When I reached the station, the train had already left. I reached the station after the train had left. I didn’t reach the station until after the train had left

The train had left before I reached the station. 我 Since before and after can indicate time sequence by their own lexical meanings,the two actions happening one after another can both be expressed by the simple past in sentences comprising a before/after-clause. Compare: The train (had)/eft before I reached the station. After the teacher (had)left the room,the children started talking. Sometimes the past perfective is used in a before-clause to lay emphasis on the incompletion of the action:

5 The train had left before I reached the station. Since before and after can indicate time sequence by their own lexical meanings, the two actions happening one after another can both be expressed by the simple past in sentences comprising a before / after-clause. Compare: The train (had) left before I reached the station. After the teacher (had) left the room, the children started talking. Sometimes the past perfective is used in a before-clause to lay emphasis on the incompletion of the action:

He offered me a drink before I had taken off my coat. He arrived before I had finished my lunch. Note:能同时使用两个过去完成时的场合极少，下面带有由 by the time引导的时间状语分句的句子是少数例外中 的一个： By the time I(had)recovered from the shock,he had disappeared. C)Use of present perfective progressive The use of the present perfective progressive (have/has been +-ing participle)has much in common with the"unfinished"use of the present perfective.Compare: I've been writing letters for an hour(and I've still got some more to do). 6

6 He offered me a drink before I had taken off my coat. He arrived before I had finished my lunch. Note: 能同时使用两个过去完成时的场合极少,下面带有由 by the time 引导的时间状语分句的句子是少数例外中 的一个: By the time I(had) recovered from the shock,he had disappeared. C) Use of present perfective progressive The use of the present perfective progressive (have / has been + -ing participle) has much in common with the “unfinished” use of the present perfective. Compare: I’ve been writing letters for an hour ( and I’ve still got some more to do)

I've been sitting in the garden(and have just come indoors). In many cases these two forms can be used interchangeably: We've been living here for ten years. We've lived here for ten years. There are cases,however,where these two forms are not interchangeable in that the present perfective progressive has also the meanings of continuousness and incompleteness.Compare: Who's been eating my dinner?(Some of it is left.") Who's eaten my dinner?(It's all gone.")

7 I’ve been sitting in the garden ( and have just come indoors). In many cases these two forms can be used interchangeably: We’ve been living here for ten years. We’ve lived here for ten years. There are cases, however, where these two forms are not interchangeable in that the present perfective progressive has also the meanings of continuousness and incompleteness. Compare: Who’s been eating my dinner? (“Some of it is left.”) Who’s eaten my dinner? (“It’s all gone.”)

Uses of past perfective progressive The past perfective progressive (had been +-ing participle)is basically similar in use of the present perfective progressive,only with time reference back-shifted to a specified past. The chief use of the past perfective progressive has also something in common with the unfinished"use of the past perfective,changeably, though in colloquial speech,the past perfective. Compare: I'd been working for three hours when he called.(collog.) I'd worked for three hours when he called. 8

8 D) Uses of past perfective progressive The past perfective progressive (had been + -ing participle) is basically similar in use of the present perfective progressive, only with time reference back-shifted to a specified past. The chief use of the past perfective progressive has also something in common with the “unfinished” use of the past perfective, changeably, though in colloquial speech, the past perfective. Compare: I’d been working for three hours when he called.(colloq.) I’d worked for three hours when he called

E)More on the use of perfective tense There are a few more points that merit our attention concerning the use of the perfective tense. a)perfective tense is often accompanied by a since-phrase or a since-clause to denote a continuous state or activity from a point in past time until now.The verb in the since clause is commonly the simple past of a dynamic verb denoting non-continuous activity. If the main or super-ordinate clause is in the

9 E) More on the use of perfective tense There are a few more points that merit our attention concerning the use of the perfective tense. a) perfective tense is often accompanied by a since-phrase or a since-clause to denote a continuous state or activity from a point in past time until now. The verb in the since￾clause is commonly the simple past of a dynamic verb denoting non-continuous activity. If the main or super-ordinate clause is in the

form ofIt be complement (denoting a time span)+since-clause",the verb be in the main clause may occur in the simple present in place of the present perfective,eg: I haven't seen him since his wedding day/since I met you. It's three months since he wrote to me. Sometimes,however,the verb in the since- clause may be the simple past of a dynamic stative(状态动词)verb,in which case the time span denoted by the since-clause is different from the present moment,we will have to use the present perfective instead of the simple past.Compare: 10

10 form of “It be + complement (denoting a time span) + since-clause”, the verb be in the main clause may occur in the simple present in place of the present perfective, eg: I haven’t seen him since his wedding day/ since I met you. It’s three months since he wrote to me. Sometimes, however, the verb in the since￾clause may be the simple past of a dynamic stative（状态动词） verb, in which case the time span denoted by the since- clause is different from the present moment, we will have to use the present perfective instead of the simple past. Compare: