class Reptilia vs reptile

class Reptilia and reptile both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Reptilia	Yes	No	No	No
reptile	Yes	No	No	No

class Reptilia (noun)	reptile (noun)
class of cold-blooded air-breathing vertebrates with completely ossified skeleton and a body usually covered with scales or horny plates; once the dominant land animals	any cold-blooded vertebrate of the class Reptilia including tortoises, turtles, snakes, lizards, alligators, crocodiles, and extinct forms