什么叫延续性动词与非延续性动词

什么叫延续性动词与非延续性动词
 
根据动作是否延续，动词可分为延续性动词和非延续性动词：延续性动词就是指所表示的动作可以延续的动词，非延续性动词就是指所表示的动作不可以延续的动词。如：
It rained for three days. 下了三天雨。(rain为延续性动词)http://yingyu.chazidian.com
He stayed away from the class for two days. 他两天没去上课。(stay为延续性动词)
I waited for you for half an hour. 我等了你半个钟头。(wait为延续性动词)
We watched the country out of the window. 从窗口我们眺望田野。(watch为延续性动词)
She arrived yesterday evening. 她是昨天晚上到的。(arrive为非延续性动词)
He left here three days ago. 他三天前就离开了。(leave为非延续性动词)
They came to a wide river. 他们来到一条宽阔的河边。(come为非延续性动词)
Mother bought us some new clothes. 妈妈给我们买了一些新衣服。(buy为非延续性动词)
I found a wallet on the sidewalk. 我在人行道上发现一个皮夹子。(find为非延续性动词)