class Aves vs order Passeriformes

class Aves and order Passeriformes both are nouns.

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

class Aves (noun)	order Passeriformes (noun)
(ornithology) the class of birds	largest order of birds comprising about half the known species: rooks, finches, sparrows, tits, warblers, robins, wrens, swallows, etc.; the four suborders are Eurylaimi, Tyranni, Menurae and Oscines or Passeres