劍橋詞典

the evening before a day when children have to go to school . Adults also use this expression informally to describe the evening before a day when they have to get up to go to work .
（兒童）上學(xué)前一天的晚上；（成人）上班前一天的晚上
I don't usually stay out this late on a school night . 明天要上班，我一般不會(huì)這麼晚還不廻家。 返回 school night