How do you say a good in Portuguese?

The direct translation of "a good" in Portuguese depends on the context and the gender of the noun it modifies:

For masculine nouns:

* um bom: This is the most common and direct translation.

* um ótimo: This means "a great" or "an excellent" and is used for a higher level of goodness.

For feminine nouns:

* uma boa: This is the most common and direct translation.

* uma ótima: This means "a great" or "an excellent" and is used for a higher level of goodness.

For plural nouns:

* bons: (masculine) or boas: (feminine)

* ótimos: (masculine) or ótimas: (feminine)

Examples:

* Um bom livro: A good book.

* Uma boa comida: A good meal.

* Bons amigos: Good friends.

* Ótima música: Excellent music.

Note: The definite article "a" is usually not translated into Portuguese unless it's part of a specific expression.