Verb + 了 (completed instance) vs Verb + 过 (past experience)
了 (le) vs 过 (guo) — a completed instance vs a past experience
了 marks that an action is completed or happened, usually tied to a specific occasion you're reporting right now: 我吃了 (I ate / I've eaten [this time]). 过 marks that an action has been experienced at least once at some point in your life — the focus is on prior EXPERIENCE, not one specific occasion: 我吃过北京烤鸭 (I've had Peking duck before, at some point). The deciding question: am I reporting a specific completed instance (→了), or asserting that this is among my life experiences, a general 'ever' (→过)? Because of this, 'have never done X' always uses 没 + verb + 过, never 没 + verb + 了 — 了 disappears entirely in the negative, while 过 stays.
Examples
- 我吃了晚饭。wǒ chī le wǎn fàn
I ate dinner.
- 我去过北京。wǒ qù guo běi jīng
I've been to Beijing before.
- 我今天早上吃了药，以前也吃过这种药。wǒ jīn tiān zǎo shang chī le yào, yǐ qián yě chī guo zhè zhǒng yào
I took medicine this morning, and I've taken this kind of medicine before too.
Common mistake
✗ Wrong: 我从来没吃了臭豆腐。
✓ Right: 我从来没吃过臭豆腐。
'Have never done X' needs the experience marker 过 after the verb — 了 disappears entirely in negative sentences with 没, it never combines with 没 the way 过 does.
Practice this pattern
Fill in the missing character:
我吃＿晚饭。
I ate dinner.