Time/Event + 后
后 (hòu) means after or later and is used to indicate that something happens following a time point or event. It is placed after a time expression or event phrase, such as 四天后 (four days later) or 发生后 (after it happened).
下课后我们一起去吃饭吧。
Xiàkè hòu wǒmen yìqǐ qù chīfàn ba.
Let's go eat together after class.
三年后,他终于回到了自己的家乡。
Sān nián hòu, tā zhōngyú huídào le zìjǐ de jiāxiāng.
Three years later, he finally returned to his hometown.
手术后你需要好好休息至少两个星期。
Shǒushù hòu nǐ xūyào hǎohāo xiūxi zhìshǎo liǎng ge xīngqī.
After the surgery, you need to rest well for at least two weeks.