class Aves vs order Procellariiformes

class Aves and order Procellariiformes both are nouns.

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

class Aves (noun)	order Procellariiformes (noun)
(ornithology) the class of birds	petrels, albatrosses, shearwaters, diving petrels