boxwood vs common box

boxwood and common box both are nouns.

Word	Noun	Adjective	Verb	Adverb
boxwood	Yes	No	No	No
common box	Yes	No	No	No

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

boxwood: evergreen shrubs or small trees
common box: large slow-growing evergreen shrub or small tree with multiple stems; extensively used for hedges or borders and topiary figures

Other hyponyms of boxwood include Buxus sempervirens, European box.

boxwood (noun)	common box (noun)
evergreen shrubs or small trees	large slow-growing evergreen shrub or small tree with multiple stems; extensively used for hedges or borders and topiary figures
very hard tough close-grained light yellow wood of the box (particularly the common box); used in delicate woodwork: musical instruments and inlays and engraving blocks