class Aves vs order Picariae

class Aves and order Picariae both are nouns.

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

class Aves (noun)	order Picariae (noun)
(ornithology) the class of birds	term used in some classifications as nearly equivalent to the order Coraciiformes