class Aves vs subphylum Vertebrata

class Aves and subphylum Vertebrata both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Aves	Yes	No	No	No
subphylum Vertebrata	Yes	No	No	No

class Aves (noun)	subphylum Vertebrata (noun)
(ornithology) the class of birds	fishes, amphibians, reptiles, birds, mammals