butterfly bush vs shrub

butterfly bush and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
butterfly bush	Yes	No	No	No
shrub	Yes	No	No	No

As nouns, shrub is a hypernym of butterfly bush; that is, shrub is a word with a broader meaning than butterfly bush:

butterfly bush: tropical shrub having clusters of white or violet or yellow flowers
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of butterfly bush include bush.

butterfly bush (noun)	shrub (noun)
tropical shrub having clusters of white or violet or yellow flowers	a low woody perennial plant usually having several major stems