rock brake vs Polypodium virgianum

rock brake and Polypodium virgianum both are nouns.

Word	Noun	Adjective	Verb	Adverb
rock brake	Yes	No	No	No
Polypodium virgianum	Yes	No	No	No

As nouns, rock brake and Polypodium virgianum are synonyms defined as:

rock brake and Polypodium virgianum: chiefly lithophytic or epiphytic fern of North America and east Asia

Other synonyms of rock brake include American wall fern, rock polypody.

rock brake (noun)	Polypodium virgianum (noun)
chiefly lithophytic or epiphytic fern of North America and east Asia	chiefly lithophytic or epiphytic fern of North America and east Asia
dwarf deciduous lithophytic ferns
any of several small lithophytic ferns of tropical and warm temperate regions