weeping willow vs willow

weeping willow and willow both are nouns.

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

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

weeping willow: willow with long drooping branches and slender leaves native to China; widely cultivated as an ornamental
willow: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of weeping willow include willow tree.

weeping willow (noun)	willow (noun)
willow with long drooping branches and slender leaves native to China; widely cultivated as an ornamental	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