A boarding school is an institution where children live within premises while being given formal instruction. The word "boarding" is used in the sense of "room and board", i.e. lodging and meals. As they have existed for many centuries, and now extend across many countries, their function and ethos varies greatly. Children in boarding schools study and live during the school year with their fellow students and possibly teachers or administrators. Some boarding schools also have day students who attend the institution by day and return off-campus to their families in the evenings.