To express a period of time: complement of duration

In Chinese, a Complement of Duration is used to indicate how long an action or state lasts.

Common duration expressions: 一刻钟 (yí kèzhōng — 15 minutes / a quarter), 半个小时 (bàn gè xiǎoshí — half an hour), 两天 (liǎng tiān — two days), 三个月 (sān gè yuè — three months).

1. Duration of a Completed Action

This structure indicates that an action lasted for a specific period of time and has already finished.

Subject + Verb + 了 + Duration + Object

她(Tā)工(gōng)作(zuò)了(le)三(sān)年(nián)。

She worked for three years.

我(Wǒ)们(men)坐(zuò)了(le)一(yí)个(gè)小(xiǎo)时(shí)公(gōng)共(gòng)汽(qì)车(chē)。

We took the bus for an hour.

你(Nǐ)怎(zěn)么(me)晚(wǎn)到(dào)了(le)一(yí)刻(kè)钟(zhōng)？

Why were you 15 minutes late?

我(Wǒ)们(men)唱(chàng)了(le)两(liǎng)个(gè)小(xiǎo)时(shí)歌(gē)。

We sang songs for two hours.

2. Duration of an Ongoing Action

Adding a second 了 (le) at the end of the sentence indicates that the action has been going on for a period of time and is still continuing.

Subject + Verb + 了 + Duration + Object + 了

我(Wǒ)学(xué)习(xí)了(le)一(yì)年(nián)汉(Hàn)语(yǔ)了(le)。

I have been studying Chinese for a year (and still am).

她(Tā)看(kàn)了(le)半(bàn)个(gè)小(xiǎo)时(shí)电(diàn)视(shì)了(le)。

She has been watching TV for half an hour.

他(Tā)们(men)游(yóu)了(le)二(èr)十(shí)分(fēn)钟(zhōng)泳(yǒng)了(le)。

They have been swimming for twenty minutes.

我(Wǒ)都(dōu)在(zài)这儿(zhèr)坐(zuò)了(le)半(bàn)个(gè)小(xiǎo)时(shí)了(le)。

I have already been sitting here for half an hour.