"The books are ours."
Translation:Os livros são nossos.
I don't agree at all. English uses the same words for 2 different functions, that doesn't mean that other languages have to "choose" only one when they have both. Portuguese can use the second meaning just by adding the definite article (o/a/os/as) and there is no reason to not accept it. Same for French (mien / le mien), for Spanish (mío / el mío), Italian (tuo / il tuo), Dutch (mijn / de mijne), and so on...
- These books are ours = estes livros são nossos / estes livros são os nossos.
- The books are ours = os livros são nossos / os livros são os nossos.
In Portuguese the words have gender masculine/feminine. When you use possessive adjectives/pronouns, you have to match them with the correct gender.
- Nosso - sing/masc
- Nossa - sing/fem
- Nossos - plural/masc
- Nossas - plural/fem.
"Books" is a masculine, plural word, so you have to use "nossos"