buckthorn vs narrow-leaved plantain

buckthorn and narrow-leaved plantain both are nouns.

Word	Noun	Adjective	Verb	Adverb
buckthorn	Yes	No	No	No
narrow-leaved plantain	Yes	No	No	No

As nouns, buckthorn and narrow-leaved plantain are synonyms defined as:

buckthorn and narrow-leaved plantain: an Old World plantain with long narrow ribbed leaves widely established in temperate regions

Other synonyms of buckthorn include English plantain, Plantago lanceolata, ribgrass, ribwort, ripple-grass.

buckthorn (noun)	narrow-leaved plantain (noun)
any shrub or small tree of the genus Bumelia	an Old World plantain with long narrow ribbed leaves widely established in temperate regions
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