Duration: how long you did it for

규칙 Duration follows the verb: 我等了半个小时。 我睡了八个小时。
With an object, take one of two routes:
· put the duration between verb and object — 我学了三年汉语。
· or repeat the verb — 我学汉语学了三年。
Never 我学了汉语三年。 To ask how long: 多长时间。