class Hexapoda vs phylum Arthropoda

class Hexapoda and phylum Arthropoda both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Hexapoda	Yes	No	No	No
phylum Arthropoda	Yes	No	No	No

class Hexapoda (noun)	phylum Arthropoda (noun)
insects; about five-sixths of all known animal species	jointed-foot invertebrates: arachnids, crustaceans, insects, millipedes, centipedes