"They are having a meal together" 或 "They are eating together" 是表示他们在一起吃饭的常用表达方式。
例句1: They are having a meal together at a nice restaurant downtown.
他们在市中心一家不错的餐厅一起吃饭。
例句2: They are eating together at the office cafeteria.
他们在办公室的餐厅一起吃饭。
这种表达方式的来源是因为这是英语中最常用的表达方式。另外, "having a meal" 或 "eating" 也是表示吃饭的常用词汇。