The particle 了

The particle 了 (le) is perhaps the most difficult aspect of Chinese grammar to understand for any student who studies this language. Just like the particle 的 and 吗, 了 doesn’t have neither tone nor meaning, but it plays a structural role within the sentence. Depending on its position, it can be of two types: aspectual or modal. Since it can be used with reference to past, present or future events, it’s important to make clear that this particle doesn’t represent the past.

了 is modal when it is placed at the end of the sentence. In this case, it indicates a change of state with respect to a previous situation, the realization of an action or the occurrence of a new condition.

天亮了。
tiānliàngle
[sky to-brighten MOD]
Day is breaking.

The particle 了 expresses a change of state: before it was dark, now day is breaking.

了 is used also with the adverb 已经 (yǐjīng) “already” and in the construction 快要…了 (kuàiyào…le) that expresses the upcoming of an action.

她已经来了。
tā yǐjīng láile
[she already to-come MOD]
She’s already here.

快要毕业了。
kuàiyào bìyèle
[soon to-graduate MOD]
I’m about to graduate.

In negative sentences with 不 (bù), the particle 了 means “not…anymore”.

我不抽烟了。
wǒ bù chōuyānle
[I not to-smoke MOD]
I don’t smoke anymore.

了 is aspectual when it is placed immediately after the verb and it expresses the realization of an action, be it related to the past or to the future.

昨天我买了一本词典。
zuótiān wǒ mǎile yī běn cídiǎn
[yesterday I to-buy ASP one QU dictionary]
Yesterday I bought a dictionary.

下了班，打电话给我！
xiàle bān, dǎ diànhuà gěi wǒ
[to-get-off ASP work to-make-a-phone-call to I]
Call me once you’ve knocked off.

When the “aspect 了” is found in the subordinate clause, followed in turn by a main clause, a relationship of temporal anteriority is formed between the action expressed by the verb linked to the perfect particle and that of the main clause, which can be introduced by the adverb 就 (jiù) “then”, indicating the consequentiality and the immediateness of the action. Depending on the presence or absence of the modal particle 了 at the end of the sentence, it is possible to understand whether the action is related to the past or to the future.

吃了饭，她就去公园散步了。
chīle fàn, tā jiù qù gōngyuán sànbùle
[to-eat ASP meal she then to-go park to-go-for-a-walk MOD]
After eating, she went for a walk in the park.

吃了饭，她就去公园散步。
chīle fàn, tā jiù qù gōngyuán sànbù
[to-eat ASP meal she then to-go park to-go-for-a-walk]
After eating, she will go for a walk in the park.

If in the sentence there is a complicated object (that is an object preceded by a number and a measure word) 了 is placed immediately after the verb, rather than at the end of the sentence.

我买了三本书。
wǒ mǎile sān běn shū
[I to-buy ASP three QU book]
I bought three books.

Lastly, the perfect 了 is not present in sentences that are negated by the adverb 没 (méi).

我没吃饭。
wǒ méi chīfàn
[I not to-eat meal]
I didn’t eat.

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