class Aves vs subphylum Craniata

class Aves and subphylum Craniata both are nouns.

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

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