笑 + 了
The verb 笑 (xiào) means 'to laugh' or 'to smile.' It is commonly used with the particle 了 to indicate that someone laughed at a specific moment or in response to something. 笑 can also combine with complements to describe the manner or extent of laughing.
她听了那个笑话之后笑了好久。
Tā tīng le nàge xiàohua zhīhòu xiào le hǎo jiǔ.
She laughed for a long time after hearing that joke.
孩子们看到小狗摔倒,都忍不住笑了起来。
Háizimen kàn dào xiǎo gǒu shuāi dǎo, dōu rěn bú zhù xiào le qǐlái.
The children couldn't help but laugh when they saw the puppy fall over.
他笑得眼泪都流出来了。
Tā xiào de yǎnlèi dōu liú chūlái le.
He laughed so hard that tears came out.