Venus'-hair fern vs maidenhair

Venus'-hair fern and maidenhair both are nouns.

Word	Noun	Adjective	Verb	Adverb
Venus'-hair fern	Yes	No	No	No
maidenhair	Yes	No	No	No

As nouns, maidenhair is a hypernym of Venus'-hair fern; that is, maidenhair is a word with a broader meaning than Venus'-hair fern:

Venus'-hair fern: delicate maidenhair fern with slender shining black leaf stalks; cosmopolitan
maidenhair: any of various small to large terrestrial ferns of the genus Adiantum having delicate palmately branched fronds

Other hypernyms of Venus'-hair fern include maidenhair fern.

Venus'-hair fern (noun)	maidenhair (noun)
delicate maidenhair fern with slender shining black leaf stalks; cosmopolitan	any of various small to large terrestrial ferns of the genus Adiantum having delicate palmately branched fronds