class Gastropoda vs order Pectinibranchia

class Gastropoda and order Pectinibranchia both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Gastropoda	Yes	No	No	No
order Pectinibranchia	Yes	No	No	No

class Gastropoda (noun)	order Pectinibranchia (noun)
snails and slugs and their relatives	large order of gastropods comprising univalve mollusks that have a single gill resembling a comb