- Date: 14th century
- 1 : an oval or circular building with rising tiers of seats ranged about an open space and used in ancient Rome especially for contests and spectacles
- 2 a : a very large auditorium
- b : a room with a gallery from which doctors and students may observe surgical operations
- c : a rising gallery in a modern theater
- d : a flat or gently sloping area surrounded by abrupt slopes
An amphitheater is an open-air venue for spectator sports, concerts, rallies, or theatrical performances. There are two similar, but distinct, types of structure for which the word 'amphitheatre' is used: Ancient amphitheatres, built by the ancient Romans, were large central performance spaces surrounded by ascending seating, and were commonly used for spectator sports; these compare more closely to modern open-air stadia. They were given this name because their shape resembled that of two theatres joined together. Modern amphitheatres (incorrectly so named, but the word has come to be used in this sense) are more typically used for theatrical or concert performances and typically feature a more traditionally theatrical-style stage with the audience only on one side, usually at an arc of less than a semicircle; these compare more closely to the theatres of ancient Greece, and have been more commonly built throughout history as performance spaces. Amphitheatres are typically man-made, though there are also geological formations used in the same manner which are known as natural amphitheatres. Special events and games were held in ancient Roman amphitheatres, such as the gladiator games.