Formal:
* "Tenha um bom dia!" (pronounced: ten-ya oom bom dia) - This is the most common and polite way to say it. It literally translates to "Have a good day!"
Informal:
* "Bom dia!" (pronounced: bom dia) - This is a more casual greeting that means "Good morning!" but can also be used to wish someone a good day.
* "Tenha um ótimo dia!" (pronounced: ten-ya oom oh-tee-moh dia) - This is a slightly more enthusiastic way of saying "Have a great day!"
* "Espero que tenha um bom dia!" (pronounced: eh-spay-roh keh ten-ya oom bom dia) - This means "I hope you have a good day!"
Other options:
* "Dia bonito!" (pronounced: dia boo-nee-toh) - This means "Beautiful day!" and is a good option if you are referring to the weather.
* "Aproveite o dia!" (pronounced: ah-proo-veh-ee-teh oh dia) - This means "Enjoy the day!"
You can also add a personal touch to your greeting by adding a name or a compliment:
* "Tenha um bom dia, Maria!" (pronounced: ten-ya oom bom dia, ma-ree-ah)
* "Que dia lindo! Tenha um bom dia!" (pronounced: keh dia leehn-doh! ten-ya oom bom dia)
The best way to say it depends on the situation and your relationship with the person you are talking to.