osier vs willow

osier and willow both are nouns.

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

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

osier: any of various willows having pliable twigs used in basketry and furniture
willow: any of numerous deciduous trees and shrubs of the genus Salix

Other hypernyms of osier include willow tree.

osier (noun)	willow (noun)
any of various willows having pliable twigs used in basketry and furniture	a textile machine having a system of revolving spikes for opening and cleaning raw textile fibers
flexible twig of a willow tree	any of numerous deciduous trees and shrubs of the genus Salix