用法
a.表示现在(指说话人说话时)正在发生的事情。
We are waiting for you.
b.习惯进行：表示长期的或重复性的动作，说话时动作未必正在进行。
Mr. Green is writing another novel.
（说话时并未在写，只处于写作的状态。)
c.表示渐变的动词有：get，grow，become，turn，run，go，begins等。
d.与always，constantly，forever等词连用，表示反复发生的动作或持续存在的状态，往往带有说话人的主观色彩。
动词ing形式变化规则
1.–ing分词的构成主动形式 被动形式 doing being done 一般式 完成式 having done having been done 否定式：not+--ing/not having(been) done 不是 having not (been) done。
2.一般式和完成式的用法--ing分词的.一般式表示和谓语动词所表示的动作同时进行的一个动作；完成式表示先于谓语动词动作之前的一个动作。如： Walking along the street, he caught sight of an old friend of his. Not having studied his lessons very hard, he failed the examinations.
3.---ing分词的被动式当－ing分词与它的逻辑主语构成被动关系时，需要用被动形式。根据－ing 分词动作发生的时间，－ing分词的被动式分为一般被动式(being done)和完成被动式(having been done),如：The question being discussed is very important. Having been praised by the teacher, he works even harder.
4.---ing分词的句法功能1)---ing分词作主语 Learning English has become a part of his life. It is no use trying to repair the ship. These holes are much too big. 2) ---ing分词作宾语 以下动词必须跟---ing分词作宾语：admit/ appreciate/avoid/consider/delay/deny/dislike/enjoy /excuse/finish/image/keep/mind/ miss/postpone/put off/practise/risk/stand/ stop/ suggest / give up/cannot help。