Wash your hands before you eat dinner.
在你吃晚餐之前要洗手。
Before I go to bed, I always brush my teeth.
在我上床睡覺之前，我總是會刷牙。
He finished his homework before his mom came home.
他在媽媽回家之前把作業寫完了。
Please turn off the lights before you leave the classroom.
在你離開教室之前，請把燈關掉。