velvet osier vs osier

velvet osier and osier both are nouns.

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

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

velvet osier: willow with long flexible twigs used in basketry
osier: any of various willows having pliable twigs used in basketry and furniture

velvet osier (noun)	osier (noun)
willow with long flexible twigs used in basketry	any of various willows having pliable twigs used in basketry and furniture
	flexible twig of a willow tree