1. A polite greeting used in the evening or night to address a group of people, wishing them a good night
As I entered the room, I said 'buenas noches a todos' to greet everyone.
Ao entrar na sala, disse 'boa noite a todos' para cumprimentar todos.
2. A farewell expression used when leaving a gathering in the evening to wish everyone a good night
Before leaving the party, she said 'buenas noches a todos'.
Antes de sair da festa, ela disse 'boa noite a todos'.