General "good":
* bom/boa (masculine/feminine) - This is the most common and versatile translation.
* Example: "This is a good book." - "Este é um bom livro."
"Good" in the sense of "well":
* bem - This is used for describing how something is done or how someone is feeling.
* Example: "I'm doing well." - "Estou bem."
"Good" as a greeting:
* bom dia - Good morning
* boa tarde - Good afternoon
* boa noite - Good evening/good night
Other variations:
* muito bom - Very good
* excelente - Excellent
* ótimo - Great
The best translation depends on the specific situation and what you want to express.