Questo libro non è mio, è suo.

to be

Breakdown of Questo libro non è mio, è suo.

• il libro: the book
• questo: this
• non: not

Questions & Answers about Questo libro non è mio, è suo.

Why are there no articles before mio and suo?

Here mio and suo function as short-form possessive pronouns (meaning “mine” and “his/hers/your formal”). In full form you’d normally say il mio or il suo, but in Italian it’s very common—especially after the verb essere—to drop the article and use just mio, tuo, suo, etc., to keep it concise.

What’s the difference between a possessive adjective and a possessive pronoun in Italian?

A possessive adjective modifies a noun and always comes before it, for example il mio libro (“my book”). A possessive pronoun replaces the entire noun phrase. In standard Italian you’d say questo è il mio (“this is mine”), but colloquially you can shorten it to questo è mio. In both cases the article (il, la, i, le) marks the pronoun, though you can drop it in short answers after essere.

Could suo here mean “his,” “her,” “its,” or “your” (formal)? How do I know which?

Yes—suo is the third-person singular possessive and also the polite second-person form. Context tells you whether it means “his,” “hers,” “its,” or “yours” (formal). If it’s still ambiguous, you can switch to a clearer form like di lui (“of him”), di lei (“of her”), or say il suo plus a name: il libro di Maria or il suo libro when you have already established who “you” is.