bay willow vs willow

bay willow and willow both are nouns.

Word	Noun	Adjective	Verb	Adverb
bay willow	Yes	No	No	No
willow	Yes	No	No	No

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

bay willow: European willow tree with shining leathery leaves; widely naturalized in the eastern United States
willow: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of bay willow include willow tree.

bay willow (noun)	willow (noun)
European willow tree with shining leathery leaves; widely naturalized in the eastern United States	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