inky cap vs inky-cap mushroom

inky cap and inky-cap mushroom both are nouns.

Word	Noun	Adjective	Verb	Adverb
inky cap	Yes	No	No	No
inky-cap mushroom	Yes	No	No	No

As nouns, inky cap and inky-cap mushroom are synonyms defined as:

inky cap and inky-cap mushroom: having a cap that melts into an inky fluid after spores have matured

Other synonyms of inky cap include Coprinus atramentarius.

inky cap (noun)	inky-cap mushroom (noun)
having a cap that melts into an inky fluid after spores have matured	having a cap that melts into an inky fluid after spores have matured