了 (le) — Completed Action

By the end of this lesson, you will use 了 correctly to mark completed actions and new situations, and distinguish between habitual and completed readings of a sentence.

Why Mandarin Needs Aspect Particles

Mandarin verbs never change form — 去 (qù — go) is identical whether you're talking about yesterday, today, or tomorrow. Instead, aspect particles attach to verbs to show how an action relates to time. 了 is the most important of these particles.

了 has two main uses that students often conflate. Understanding the difference is essential.

Use 1: Verbal 了 — Completed Action

Position: immediately after the verb (sometimes called 了₁ or V+了)

When 了 follows a verb, it signals that the action was completed. This is not quite the same as the English past tense — it's more about completion than time.

Chinese	Pinyin	English
我吃了饭。	Wǒ chī le fàn.	I ate (the meal / a meal).
他买了一本书。	Tā mǎi le yī běn shū.	He bought a book.
她喝了三杯茶。	Tā hē le sān bēi chá.	She drank three cups of tea.
我们看了那部电影。	Wǒmen kàn le nà bù diànyǐng.	We watched that film.

The Object After Verbal 了

When 了 is used this way, the object is typically specified — it usually has a number, measure word, demonstrative (这/那), or modifier attached:

• 我吃了饭。 (correct — 饭 as a general object is acceptable)
• 我吃了三碗饭。 (more typical — three bowls of rice)

A bare, unmodified object after verbal 了 often sounds incomplete without a sentence-final particle. Compare:

我买了书。 (sounds slightly incomplete in isolation) 我买了书了。 (sounds complete — two 了s are fine) 我买了一本书。 (the number makes it natural)

Use 2: Sentence-Final 了 — New Situation

Position: at the end of the sentence (sometimes called 了₂ or modal 了)

Sentence-final 了 signals a change of state or a new situation that is now relevant. It's not about completion — it's about something becoming true that wasn't true before.

Chinese	Pinyin	English