Completed-action 了 (verb + 了)
A2 完成体助词「了」 18 / 56
In short
Put 了 (le) right after the verb to mark that an action was completed or realized: 我买了一本书 (Wǒ mǎi le yì běn shū) = I bought a book. This 了 signals completion, not past tense - it can even sit inside a future plan. When the sentence ends on the object, that object normally carries a number + measure word (一本, 两个). To say the action did not happen, switch to 没(有) and drop 了 entirely: 我没买书 (Wǒ méi mǎi shū).
The rule
Chinese has no verb tenses. Instead it marks aspect - whether an action is finished, ongoing, experienced. The particle 了 (le) placed immediately after a verb is the completed-action (完成体, wánchéngtǐ) marker: it says the event was carried through to completion.
Step 1 - Where it goes. 了 attaches directly to the verb, and the object follows:
Subject + Verb + 了 + (number + measure word +) Object
我喝了一杯咖啡。 (Wǒ hē le yì bēi kāfēi.) = I drank a cup of coffee. Nothing comes between the verb and 了.
Step 2 - Completion, not “past tense.” 了 marks that the action is complete, which is often but not always in the past. It happily lives in a future frame: 我吃了饭就走。 (Wǒ chī le fàn jiù zǒu.) = I’ll leave once I’ve eaten. Here the eating hasn’t happened yet - 了 just says “after that action is finished.” Do not reach for 了 every time you translate an English past-tense verb; reach for it when you mean the action reached its end point.
Step 3 - Give the object a quantity. A verb + 了 followed by a bare, unmodified noun sounds unfinished, as if the listener is waiting for more (我买了书… feels like “I bought a book and then…”). To make a complete, self-standing statement, add a number + measure word, or make the object specific: 我买了一本书 (bought a book), 我买了那本书 (Wǒ mǎi le nà běn shū, bought that book). The number can be 一 (yī, one) or any other: 两个, 三杯, 几本. The one place a bare object is right is where a second clause finishes the sentence for you - 我吃了饭就走 (Step 2) - since there the “and then…” a bare noun promises actually arrives, and quantifying it is what goes wrong (我下了一节课就回家).
Step 4 - No object? 了 sits at the end. If the verb has no object, 了 lands at the very end of the clause: 我吃了。 (Wǒ chī le.) = I’ve eaten. This is still the verb-suffix 了. It occupies the same slot as the sentence-final 了 of change-of-state (a different particle, taught in Sentence-final 了 and change of state) - here just take it as “verb + 了, object left out.”
Step 5 - Negation removes 了. To say the action did not happen, use 没(有) (méiyǒu) before the verb and delete 了: 我没买那本书。 (Wǒ méi mǎi nà běn shū.) = I didn’t buy that book. Because 没 already means “the event did not occur,” keeping 了 would be a contradiction. (The 不 / 没 split itself is in Negation with 不 and 没(有).)
Step 6 - Asking about completion. Add 吗 to the statement, or tack on 没有 for an A-not-A question: 你买了那本书吗？ / 你买了没有？ (Nǐ mǎi le méiyǒu?) = Did you buy it (or not)?
Forms & patterns
The core patterns, by object type:
| Pattern | Example | Meaning |
|---|---|---|
| S + V + 了 + Num + MW + Obj | 我买了一本书 (Wǒ mǎi le yì běn shū) | I bought a book |
| S + V + 了 + specific Obj | 我吃了那个苹果 (Wǒ chī le nàge píngguǒ) | I ate that apple |
| S + V + 了 (no object) | 我吃了 (Wǒ chī le) | I’ve eaten |
| S + V + 了 + Obj₁, 就 + V₂ (sequence) | 我下了课就回家 (Wǒ xià le kè jiù huí jiā) | I’ll go home as soon as class is over |
The same verb across statement, negation and question - note that 了 disappears under negation:
| Function | Form | Pinyin | Meaning |
|---|---|---|---|
| Statement | 我买了那件衣服。 | Wǒ mǎi le nà jiàn yīfu. | I bought that piece of clothing. |
| Negation | 我没买那件衣服。 | Wǒ méi mǎi nà jiàn yīfu. | I didn’t buy that piece of clothing. |
| Yes/no question | 你买了那件衣服吗？ | Nǐ mǎi le nà jiàn yīfu ma? | Did you buy that piece of clothing? |
| A-not-A question | 你买了那件衣服没有？ | Nǐ mǎi le nà jiàn yīfu méiyǒu? | Did you buy it or not? |
Examples
- 我买了一本书。 (Wǒ mǎi le yì běn shū.) - I bought a book.
- 她喝了一杯咖啡。 (Tā hē le yì bēi kāfēi.) - She drank a cup of coffee.
- 我们看了那部电影。 (Wǒmen kàn le nà bù diànyǐng.) - We watched that movie.
- 他吃了两个苹果。 (Tā chī le liǎng gè píngguǒ.) - He ate two apples.
- 昨天我买了一件衣服。 (Zuótiān wǒ mǎi le yí jiàn yīfu.) - Yesterday I bought a piece of clothing.
- 我吃了饭就去上班。 (Wǒ chī le fàn jiù qù shàngbān.) - I’ll go to work once I’ve eaten.
- 你喝了几杯？ (Nǐ hē le jǐ bēi?) - How many cups did you drink?
- 我没买那本书。 (Wǒ méi mǎi nà běn shū.) - I didn’t buy that book.
Common mistakes
- 我买书。 (meaning “I bought a book”) -> 我买了一本书。 (Wǒ mǎi le yì běn shū.) - a completed action needs verb + 了; the bare verb reads as a habit or a general statement.
- 我没买了衣服。 -> 我没买衣服。 (Wǒ méi mǎi yīfu.) - 没 already marks the action as not having happened, so 了 must be dropped.
- 我买了书。 (as a full, closed statement) -> 我买了三本书。 (Wǒ mǎi le sān běn shū.) - a bare noun after 了 leaves the sentence hanging; give the object a number + measure word (or make it specific).
- 我了吃饭。 -> 我吃了饭。 (Wǒ chī le fàn.) - 了 attaches after the verb, never before it.
Tips
- Think “completion switch,” not “past tense.” If the action reaches its end point - even in a future plan (吃了饭就走) - 了 fits; if you just mean a habit or a state that happened to be in the past, it does not.
- Build the reflex V + 了 + 一 + measure word + noun: 买了一本书, 喝了一杯茶, 看了一个电影. The quantity is what lets the sentence stand on its own.
- For life experience (“Have you ever been to China?”) Mandarin uses 过 (guo), not 了 - that is a different aspect, covered in Experiential aspect 过.
- When the verb has no object, 了 rides at the sentence end (我吃了), which looks identical to the change-of-state 了. They are two different particles; keep them apart via Sentence-final 了 and change of state.