auditorium

noun (plural auditoriums or auditoria /-rɪə/)

• 1the part of a theatre, concert hall, or other public building in which the audience sits: the stage was small and the auditorium had only 366 seats

• 2chiefly North American a large building or hall used for public gatherings, typically speeches or stage performances: the National Indoor Arena is a magnificent auditorium and one of Britain’s premier indoor venues