wall fern vs polypody

wall fern and polypody both are nouns.

Word	Noun	Adjective	Verb	Adverb
wall fern	Yes	No	No	No
polypody	Yes	No	No	No

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

wall fern: mat-forming lithophytic or terrestrial fern with creeping rootstocks and large pinnatifid fronds found throughout North America and Europe and Africa and east Asia
polypody: any of numerous ferns of the genus Polypodium

wall fern (noun)	polypody (noun)
mat-forming lithophytic or terrestrial fern with creeping rootstocks and large pinnatifid fronds found throughout North America and Europe and Africa and east Asia	any of numerous ferns of the genus Polypodium