coliseum vs sports stadium

coliseum and sports stadium both are nouns.

Word	Noun	Adjective	Verb	Adverb
coliseum	Yes	No	No	No
sports stadium	Yes	No	No	No

As nouns, sports stadium is a hypernym of coliseum; that is, sports stadium is a word with a broader meaning than coliseum:

coliseum: an oval large stadium with tiers of seats; an arena in which contests and spectacles are held
sports stadium: a large structure for open-air sports or entertainments

Other hypernyms of coliseum include arena, bowl, stadium.

coliseum (noun)	sports stadium (noun)
an oval large stadium with tiers of seats; an arena in which contests and spectacles are held	a large structure for open-air sports or entertainments