class Filicopsida vs family Dennstaedtiaceae

class Filicopsida and family Dennstaedtiaceae both are nouns.

Word	Noun	Adjective	Verb	Adverb
class Filicopsida	Yes	No	No	No
family Dennstaedtiaceae	Yes	No	No	No

class Filicopsida (noun)	family Dennstaedtiaceae (noun)
ferns	one of a number of families into which Polypodiaceae has been subdivided in some classification systems, it is one of fifteen families of ferns (Dennstaedtiaceae)