common myrtle vs myrtle

common myrtle and myrtle both are nouns.

Word	Noun	Adjective	Verb	Adverb
common myrtle	Yes	No	No	No
myrtle	Yes	No	No	No

As nouns, myrtle is a hypernym of common myrtle; that is, myrtle is a word with a broader meaning than common myrtle:

common myrtle: European shrub with white or rosy flowers followed by black berries
myrtle: any evergreen shrub or tree of the genus Myrtus

common myrtle (noun)	myrtle (noun)
European shrub with white or rosy flowers followed by black berries	any evergreen shrub or tree of the genus Myrtus
	widely cultivated as a groundcover for its dark green shiny leaves and usually blue-violet flowers