This is the 457th most frequent Italian word.
tuo
"Your" (singular, informal).
Here, 'tuo' serves as a possessive adjective, modifying 'fratello' (brother) to signify that the brother belongs to 'tu' (you).
Ho incontrato tuo fratello ieri.
I met your brother yesterday.
In this example, 'tuo' again functions as a possessive adjective to indicate ownership of 'cane' (dog), asking if the dog belongs to 'tu' (you).
È questo il tuo cane?
Is this your dog?
In this sentence, 'tuo' is used as a possessive adjective to indicate ownership, modifying the noun 'libro' (book) and denoting that it belongs to 'tu' (you).