class Crustacea vs subclass Malacostraca

class Crustacea and subclass Malacostraca both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Crustacea	Yes	No	No	No
subclass Malacostraca	Yes	No	No	No

class Crustacea (noun)	subclass Malacostraca (noun)
class of mandibulate arthropods including: lobsters, crabs, shrimps, woodlice, barnacles, decapods, water fleas	largest subclass of Crustacea including most of the well-known marine, freshwater, and terrestrial crustaceans: crabs, lobsters, shrimps, sow bugs, beach flies