class Aves vs order Cuculiformes

class Aves and order Cuculiformes both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Aves	Yes	No	No	No
order Cuculiformes	Yes	No	No	No

class Aves (noun)	order Cuculiformes (noun)
(ornithology) the class of birds	cuckoos, touracos, etc.