了 (le): completion and change
The most used — and most misused — particle in Chinese: what 了 actually marks, and why it is not past tense.
Not past tense
The first thing to unlearn: 了 does not mean past. Chinese verbs never change form for time — time comes from words like 昨天 (yesterday) or 明天 (tomorrow). What 了 marks is that an action is complete, or that a situation has changed. Both can sit in the past, the present or the future.
我吃了三个包子。
明天我下了课去找你。
了 after the verb: something got completed
Placed right after a verb, 了 says the action ran to completion. It usually wants a measured object — 三个包子, 两杯茶 — because completing something is easiest to state when the something has a size.
她买了两本书。
我们看了一个电影。
了 at the end: the situation is new
At the end of a sentence, 了 announces a change of state: something is true now that wasn't before. This is the 了 of 下雨了 — not "it rained", but "it's raining (and it wasn't a moment ago)".
下雨了。
我饿了。
他不喝咖啡了。
Where 了 refuses to go
Negate a completed action with 没, and 了 disappears — 没 already says the completion didn't happen. And with both 了s in one sentence, an action reaches into the present: 住了两年了 means the two years are still counting.
我昨天没去。
我在北京住了两年了。
Look up the word: 了 · All grammar guides
Patterns stick when you meet them in sentences you can read. The app drills each one at i+1, scheduled by FSRS.
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