An amphitheatre (British English) or amphitheater (American English; both /ˈæmfɪˌθiːətər/) is an open-air venue used for entertainment, performances, and sports. The term derives from the ancient Greek ἀμφιθέατρον (amphitheatron), from ἀμφί (amphi), meaning "on both sides" or "around" and θέατρον (théātron), meaning "place for viewing". Modern parlance uses "amphitheatre" for any structure with sloping seating, including theatre-style stages with spectator seating on only one side, theatres in the round, and stadia. They can be indoor or outdoor.