Expressing duration with "le"
After reading this primer on one of the many uses of 了 (le), you will have gotten a good grasp on how to express the duration of something.
Saying how long you did something for in Chinese can seem tricky, as there is no preposition as in English. Instead it's all about word order:
Subj. + Verb + 了 + Duration + Obj.
So 了 (le) is placed after the verb (to indicate that the action is completed), followed by the duration. This is how you talk about the duration of completed actions.
- 他 学 了 一 年 中文。He studied Chinese for a year.
- 我 看 了 一 个 晚上 书。I read books all evening.
- 他 在 Google 做 了 八 年 经理。 He worked as a manager at Google for eight years.
- 妈妈 看 了 一 天 电视。Mom watched TV all day.
- 我们 坐 了 十 五 个 小时 飞机 去 美国。We took a fifteen hour flight to the United States.
To express completed definitely
Note that the pattern above can be used to express the duration of completed actions which are no longer in progress, although strictly speaking, it's not entirely clear if the actions are still ongoing or not. To indicate that the actions are definitely completed, a time word may be inserted into the sentence to indicate that you're talking about an event in the past:
Subj. + [Time Word] + Verb + 了 + Duration + Obj.
- 你 刚才 上 了 半 个 小时 厕所。 You were just in the bathroom for half an hour.
- 他 今天 喝 了 一 个 晚上 酒。 He drank alcohol all night.
- 我 昨天 玩 了 一 个 下午 游戏。Yesterday, I played games all afternoon.
- 上 个 周末 我 和 老公 开 了 三 个 小时 车 回 老家。Last weekend, my husband and I drove three hours to our hometown.
- 昨天 他 写 了 一 天 作业。 He did his homework all day yesterday.
To indicate that the action is definitely still in progress, use a slightly different pattern.