au·di·to·ri·um / ˌôdiˈtôrēəm/ • n. (pl. -to·ri·ums or -to·ri·a / -ˈtôrēə/ ) 1. the part of a theater, concert hall, or other public building in which the audience sits.2. a large building or hall used for public gatherings, typically concerts or sports events. ∎  a large room for such gatherings, esp. in a school.

auditorium (pl. auditoria).
1. The nave of a church (see auditory).

2. Part of a concert-hall, theatre, etc., occupied by the audience.

3. Reception-room in a monastery.

4. Building for concerts, theatrical performances, etc.