Salix pyrifolia vs willow

Salix pyrifolia and willow both are nouns.

Word	Noun	Adjective	Verb	Adverb
Salix pyrifolia	Yes	No	No	No
willow	Yes	No	No	No

As nouns, willow is a hypernym of Salix pyrifolia; that is, willow is a word with a broader meaning than Salix pyrifolia:

Salix pyrifolia: small shrubby tree of eastern North America having leaves exuding an odor of balsam when crushed
willow: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of Salix pyrifolia include willow tree.

Salix pyrifolia (noun)	willow (noun)
small shrubby tree of eastern North America having leaves exuding an odor of balsam when crushed	a textile machine having a system of revolving spikes for opening and cleaning raw textile fibers
	any of numerous deciduous trees and shrubs of the genus Salix