晚上背单词的英语常用表达有：

study vocabulary in the evening
review vocabulary at night
practice vocabulary at night

这些表达的来源都是来自英语语言本身，用来表示在晚上的时候学习或复习单词。

一些英文例句和中文翻译如下：

I usually study vocabulary in the evening after dinner. (我通常在晚饭后晚上学习单词。)
She reviews vocabulary at night before going to bed. (她晚上睡觉前复习单词。)
He practices vocabulary at night to improve his Engpsh skills. (他晚上练习单词来提高英语水平。)