What is a definition of the word 'arena'?

An arena in ancient times was the central space in a Roman amphitheater that was covered with sand and was used for public entertainments such as mock sea battles and gladiatorial fights. A modern definition would be that of an indoor stadium or sports hall. Modern arenas are multi-purpose auditoriums in which the central performance space can be used for a wide variety of activities such as Basketball, Ice Hockey, concerts, circuses, and even political conventions and religious ceremonies. Figuratively, the Word "arena" can be used to refer to any field of human activity or line of work, especially where there is competition involved.