Formal:
* Para sempre: This is the most common and literal translation of "forever." It's used in both formal and informal settings.
* Eternamente: This means "eternally" and is often used in more poetic or formal contexts.
Informal:
* Para todo o sempre: This is a more emphatic way of saying "forever" and is often used in informal contexts.
* Até o fim dos tempos: This means "until the end of time" and is a very strong and emphatic way to express "forever."
Other:
* Para sempre e sempre: This is another emphatic way of saying "forever" and is often used to emphasize the duration of something.
* Para a eternidade: This means "for eternity" and is a very strong and formal way to express "forever."
The best way to say "forever" in Portuguese depends on the specific context and the desired level of formality.