Formal:
* Boa noite (pronounced "boah noy-chee") - This is the most common and general way to say good night.
Informal:
* Boa noite (pronounced "boah noy-chee") - You can also use the formal "boa noite" in informal situations.
* Boa noite (pronounced "boah noy-chee") - Sometimes people shorten it to just "Boa noite".
More specific:
* Durma bem (pronounced "door-mah bem") - This means "sleep well".
* Tenha uma boa noite (pronounced "ten-ya oo-ma boah noy-chee") - This means "have a good night".
Note: The choice of which phrase to use depends on the situation and your relationship with the person.