Duration: V + (了) + time span
补语 / complements (时量补语)
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
Verb + (了) + duration (+ 的) + Object / V + O + V + duration
To say how long an action lasts, Chinese puts the duration after the verb (unlike a point in time, which goes before): 我学了两年 = I studied for two years.
With an object, two options:
1) V + duration + (的) + O: 我看了两个小时(的)书.
2) V + O + V + duration (repeat the verb): 我看书看了两个小时.
If it's still going on now, add a final 了: 我头疼了三天了 (I've had a headache for three days, and still do).
Examples
我咳嗽了一个星期了。
Wǒ késou le yí ge xīngqī le.I've been coughing for a week.
昨天我睡了十个小时。
Zuótiān wǒ shuìle shí ge xiǎoshí.I slept ten hours yesterday.
他学中文学了三年。
Tā xué Zhōngwén xuéle sān nián.He studied Chinese for three years.
请等一会儿。
Qǐng děng yíhuìr.Please wait a moment.
Common mistakes
✗ 我两个小时看书 → ✓ 我看了两个小时书 (duration comes after the verb).
✗ 我学中文了三年 → ✓ 我学了三年中文 / 我学中文学了三年.