myrtle vs common myrtle

myrtle and common myrtle both are nouns.

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

As nouns, common myrtle is a hyponym of myrtle; that is, common myrtle is a word with a more specific, narrower meaning than myrtle:

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

Other hyponyms of myrtle include Myrtus communis.

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