"后天"的英语表达是 "the day after tomorrow"。这个词组来源于英语中对时间的描述方式，"tomorrow" 是 "明天"的意思，"the day after" 是 "后天"的意思。
例句：
I will see you the day after tomorrow. (我将在后天见到你。)
The movie is showing the day after tomorrow. (电影将在后天上映。)
I will finish my work the day after tomorrow. (我将在后天完成我的工作。)