What did you do yesterday?

The 了 completion marker

In Chinese, 了 (le) placed right after a verb signals that an action was completed. It is the core way to talk about past events.

Structure

• Subject + Verb + 了 + Object
• 我吃了饭。(Wǒ chī le fàn.) — I ate (the meal).
• 她去了超市。(Tā qù le chāoshì.) — She went to the supermarket.

Time expressions come first

In Chinese, time words go before the verb, not at the end like in English.

• 昨天 (zuótiān) 我看了电影。— Yesterday I watched a movie.
• 上个星期 (shàng ge xīngqī) 他买了新手机。— Last week he bought a new phone.

Negation of past actions

To say you did NOT do something, use 没有 (méiyǒu) or just 没 (méi) — and drop 了:

• 我没吃早饭。(Wǒ méi chī zǎofàn.) — I didn't eat breakfast.
• 她昨天没来。(Tā zuótiān méi lái.) — She didn't come yesterday.

Key rule: 了 goes directly after the verb, never at the end of the sentence.