order Insessores vs class Aves

order Insessores and class Aves both are nouns.

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

order Insessores (noun)	class Aves (noun)
a bird with feet adapted for perching (as on tree branches); this order is now generally abandoned by taxonomists	(ornithology) the class of birds