This is the 322nd most frequent Italian word.
noi
"We."
The word 'noi' is a pronoun used as an object of the preposition 'per', meaning 'us' and indicating the recipient of the book.
Questo libro è per noi, non per loro.
This book is for us, not for them.
Here 'noi' again is a subject pronoun used to emphasize the group doing the action.
Se noi studiamo, otterremo ottimi voti.
If we study, we will get excellent grades.
The word 'noi' is a pronoun used as the subject of the sentence, meaning 'we' and indicating the speaker and their group.