arena vs environment

arena and environment both are nouns.

Word	Noun	Adjective	Verb	Adverb
arena	Yes	No	No	No
environment	Yes	No	No	No

As nouns, environment is a hypernym of arena; that is, environment is a word with a broader meaning than arena:

arena (noun)	environment (noun)
a playing field where sports events take place	the area in which something exists or lives
a large structure for open-air sports or entertainments	the totality of surrounding conditions
the central area of an ancient Roman amphitheater where contests and spectacles were held; especially an area that was strewn with sand
a particular environment or walk of life