button fern vs fern

button fern and fern both are nouns.

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

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

button fern: Jamaican fern having round buttonlike bulbils
fern: any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores

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

button fern: fern of New Zealand and Australia having trailing fronds with dark green buttonlike leaflets
fern: any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores

button fern (noun)	fern (noun)
Jamaican fern having round buttonlike bulbils	any of numerous flowerless and seedless vascular plants having true roots from a rhizome and fronds that uncurl upward; reproduce by spores
fern of New Zealand and Australia having trailing fronds with dark green buttonlike leaflets