1. As a modal particle, “了” is used at the end of a sentence to indicate something has already happened.
他去学校了。（Tā qù xuéxiào le.）
He went to school.
我们结婚一年了。（Wǒmen jiéhūn yī nián le.）
We got married for 1 year.
我和他去看电影了。（Wǒ hé tā qù kàn diànyǐng le.）
He and I went to watch movie.
2. As a dynamic auxiliary, “了” is used after verbs to refer to the completion of an action. It`s often followed by quantifiers.
去年我看了10本书。（Qùnián wǒ kànle 10 běn shū.）
I read 10 books last year.
我买了很多衣服。（Wǒ mǎile hěnduō yīfu.）
I bought lots of clothes.
我吃了午饭。（Wǒ chīle wǔfàn.）
I have had lunch.
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