class Crustacea vs crustacean

class Crustacea and crustacean both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Crustacea	Yes	No	No	No
crustacean	Yes	Yes	No	No

class Crustacea (noun)	crustacean (noun)
class of mandibulate arthropods including: lobsters, crabs, shrimps, woodlice, barnacles, decapods, water fleas	any mainly aquatic arthropod usually having a segmented body and chitinous exoskeleton

class Crustacea (adjective)	crustacean (adjective)
	of or belonging to the class Crustacea