1. A polite expression wishing someone a good night's sleep; used as a farewell before bedtime
Good night, sleep well! See you tomorrow.
Durmam bem! Vejo vocês amanhã.
2. An imperative form addressing multiple people or using formal/plural 'vocês', expressing the desire for restful sleep
Everyone, sleep well and rest up for the big day ahead.
Durmam bem e descansem para o grande dia.