Arena and Backstop

Arena noun - A large room or building for enclosed public gatherings.

Backstop and arena are semantically related. In some cases you can use "Backstop" instead a noun "Arena".

Backstop noun - (baseball) a fence or screen (as behind home plate) to prevent the ball from traveling out of the playing field.

Arena and backstop are semantically related. Sometimes you can use "Arena" instead a noun "Backstop".