Italian possessive adjectives: mio, tuo, suo and the article

In Italian: Aggettivi possessivi

Unlike English, an Italian possessive normally keeps its article: il mio libro, la mia casa, i miei amici.

The possessive agrees with the thing owned, never with the owner — which is why la sua macchina is his car and her car alike, and only context tells them apart.

The exception worth memorising is a single family member, which drops the article: mia madre, tuo fratello, suo marito. Make it plural or add an adjective and the article comes back: i miei fratelli, la mia sorella maggiore.