This is the 29th most frequent Italian word.
sua
"His," "her," "its," or "your" (formal), depending on context.
Here, 'sua' changes form to 'suo,' indicating possession, correlated in gender and number with 'libro' (masculine singular) for 'his.'
Lui legge il suo libro: è interessante.
He reads his book: it's interesting.
In this example, 'sua' is used in an impersonal generic sense, referring to any student's possession.
Ogni studente deve portare la sua penna.
Every student must bring their pen.
In this sentence, 'sua' is a possessive adjective referring to 'her' and describes ownership of the house.