Formal:
* Tudo bem: This is the most common and versatile way to say "ok." It can be used in most situations, even when addressing someone older or in a position of authority. It literally means "everything is good."
* Está bem: This is another formal option, meaning "it's good" or "it's fine."
Informal:
* Ok: You can also simply say "ok," just like in English.
* Beleza: This is a very common and informal way to say "ok," meaning "beauty" or "goodness."
* Tá: This is a super informal way to say "ok," meaning "it's like that" or "it's going." It's often used between friends and family.
* De boas: This is another informal option, meaning "good" or "chill."
The best way to choose the right phrase is to consider the context and your relationship with the person you are talking to.