coffeeberry vs buckthorn

coffeeberry and buckthorn both are nouns.

Word	Noun	Adjective	Verb	Adverb
coffeeberry	Yes	No	No	No
buckthorn	Yes	No	No	No

As nouns, buckthorn is a hypernym of coffeeberry; that is, buckthorn is a word with a broader meaning than coffeeberry:

coffeeberry: evergreen shrub of western United States bearing small red or black fruits
buckthorn: a shrub or shrubby tree of the genus Rhamnus; fruits are source of yellow dyes or pigments

coffeeberry (noun)	buckthorn (noun)
evergreen shrub of western United States bearing small red or black fruits	any shrub or small tree of the genus Bumelia
	a shrub or shrubby tree of the genus Rhamnus; fruits are source of yellow dyes or pigments
	an Old World plantain with long narrow ribbed leaves widely established in temperate regions