class Gasteropoda vs order Pectinibranchia

class Gasteropoda and order Pectinibranchia both are nouns.

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

class Gasteropoda (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