Pieris japonica vs shrub

Pieris japonica and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pieris japonica	Yes	No	No	No
shrub	Yes	No	No	No

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

Pieris japonica: broad-leaved evergreen Asiatic shrub with glossy leaves and drooping clusters of white flowers
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of Pieris japonica include bush.

Pieris japonica (noun)	shrub (noun)
broad-leaved evergreen Asiatic shrub with glossy leaves and drooping clusters of white flowers	a low woody perennial plant usually having several major stems