Isoetaceae vs fern family

Isoetaceae and fern family both are nouns.

Word	Noun	Adjective	Verb	Adverb
Isoetaceae	Yes	No	No	No
fern family	Yes	No	No	No

As nouns, fern family is a hypernym of Isoetaceae; that is, fern family is a word with a broader meaning than Isoetaceae:

Isoetaceae (noun)	fern family (noun)
quillworts; coextensive with the genus Isoetes	families of ferns and fern allies