Formal:
* Olá: This is the most common and polite way to say "hello."
* Bom dia: (Good morning) Used from sunrise to noon.
* Boa tarde: (Good afternoon) Used from noon to sunset.
* Boa noite: (Good evening) Used from sunset until late at night.
Informal:
* Oi: This is a more casual and friendly way to say "hello."
* E aí: (What's up?) This is a very casual and informal greeting.
* Fala: (Speak) This is a very informal greeting, often used between friends.
Other Options:
* Salve: A slang greeting, similar to "What's up?"
* E aí, tudo bem? (Hey, how are you?) A common way to say hello and inquire about someone's well-being.
Remember that the best way to say "hi" in Brazilian depends on the situation and your relationship with the person you are greeting.