Lewis & Short

amphĭthĕātrum, i, n., = ἀμφιθέατρον, an amphitheatre, a circular or oval building in which each successive seat, raised above the last, furnished an unobstructed view. From its shape it was sometimes called circus. In Rome it was used for public spectacles: for combats of wild beasts and of ships, but most frequently for gladiatorial shows. It was at first built of wood, but afterwards of stone, and with great splendor. The largest one, designed by Augustus, but begun by Vespasian and finished by Titus, was called the Amphitheatrum Florium, or, since the time of Bede, the Colosseum or Colisœum, perhaps from the Colossus of Nero, which stood close by. This is said to have held eighty-seven thousand spectators, Plin. 19, 1, 6, § 24; Tac. A. 4, 62; id. H. 2, 67; Suet. Aug. 29; id. Calig. 18; id. Vesp. 9; id. Tit. 7; id. Tib. 40; id. Ner. 12; Isid. 15, 2, 35, p. 471 al.; cf. Smith, Class. Dict.