class Hexapoda vs subclass Exopterygota

class Hexapoda and subclass Exopterygota both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Hexapoda	Yes	No	No	No
subclass Exopterygota	Yes	No	No	No

class Hexapoda (noun)	subclass Exopterygota (noun)
insects; about five-sixths of all known animal species	subclass of insects characterized by gradual and usually incomplete metamorphosis