Arena

pl. Arenas, Arenæ

1. The area in the central part of an amphitheater, in which the gladiators fought and other shows were exhibited; -- so called because it was covered with sand. (Rom. Antiq.)
2. Any place of public contest or exertion; any sphere of action; as, the arenaof debate; the arena of life.
3. “Sand” or “gravel” in the kidneys. (Med.)