Learn That Word

Synonyms for Arena (same or very similar meaning)

WordNet sense 1 (a particular environment or walk of life):
area, domain, field, orbit, sphere

WordNet sense 2 (a large structure for open-air sports or entertainments):
bowl, stadium, sports stadium

WordNet sense 3 (a playing field where sports events take place):
scene of action

From the ODE community, based on WordNetadd/edit