wood fern vs fern

wood fern and fern both are nouns.

Word	Noun	Adjective	Verb	Adverb
wood fern	Yes	No	No	No
fern	Yes	No	No	No

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

wood fern: any of various ferns of the genus Dryopteris
fern: any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores

wood fern (noun)	fern (noun)
any of various ferns of the genus Dryopteris	any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores