class Hexapoda vs order Diptera

class Hexapoda and order Diptera both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Hexapoda	Yes	No	No	No
order Diptera	Yes	No	No	No

class Hexapoda (noun)	order Diptera (noun)
insects; about five-sixths of all known animal species	a large order of insects having a single pair of wings and sucking or piercing mouths; includes true flies and mosquitoes and gnats and crane flies