持续性动词和瞬间性动词

1. 持续性动词
持续性动词表示持续的行为或状态，常见的有
be, clean, do, drink, drive, eat, fly, have, keep, know, learn, lie, live, play, rain, read, run, sing, sit, sleep, speak, smoke, snow, stand, stay, study, talk, wait, walk, wear, work, write

1) 持续性动词可用于现在完成时态，并可与表示一段时间的状语连用。一段时间的状语如: for three years, since last month, how long, during the past two months 等。如:
I know her very well because we have been friends for over ten years. 我很了解她，因为我们已是十年的老友。
I have learned English since I came here. 自从我来到这儿就学英语了。

2) 持续性动词不能与表示短暂的时间状语(点时间)连用。如: It rained at six yesterday morning. 这句话语法上是有错的。因为 at six 表示“点时间”，而rain 是持续性动词。如果要用持续性动词表示一时短暂的动作，可以在其前加上come to, begin to, start to, get to等。　
It started to rain at six yesterday morning. 昨天上午6点开始下雨。
When did you get to know him? 你什么时候认识他的。

2. 瞬间性动词
瞬间性动词表示短暂的（不能持续的）动作。常见的有：
admit, arrive, become, begin, borrow, buy, break, close, come, die, enter, fall, find, finish, get on, get off, get to, get up, go, hear, happen, hit, join, jump, leave, lend, lose, marry, open, put, reach, start, set out, stop, take away,

1) 由于瞬间性动词表示短暂的动作，因而不能与表示一段时间的状语连用。(但这种限制只是对于肯定句而言, 否定句则没有这种限制。)

误: She has died for three years.
正: She has been dead for three years. 她死了三年了。

误: How long have you come here?
正: How long have you been here? 你来多久了?

注:
a) 如果要用瞬间性动词表达上面的“她死了三年了。”这一句，可以采用以下的句式：
正: She died three years ago.
正: It is three years since she died.
正: Three years has passed since she died.

b) 当句子是否定句时，瞬间性动词与表示一段时间的状语连用是可以的。如:
正: I haven't heard from her for three weeks. 我有三周没收到她的来信了。
正: We haven't come here for ages. 我们多年没来这里了。
正: We didn't find our seats until the play had begun. 我们直到戏开始才找到位子。

2) 瞬间性动词一般不用于while引导的时间状语从句中，而宜用于 when 或 as 引导的时间状语从句中。这是因为while表示的是一段较长的时间或过程。

误: Please look after my little dog while we left.
正: Please look after my little dog while we are away. 我们外出时，请照顾我的小狗。

误: While I came home she was cooking dinner.
正: When I came home she was cooking dinner. 当我到家时，她在做饭。