hollow vs unsubstantial

hollow is a noun but unsubstantial is not a noun.

Word	Noun	Adjective	Verb	Adverb
hollow	Yes	Yes	Yes	No
unsubstantial	No	Yes	No	No

hollow (noun)	unsubstantial (noun)
a depression hollowed out of solid matter
a small valley between mountains
a cavity or space in something

hollow (adjective)	unsubstantial (adjective)
not solid; having a space or gap or cavity	lacking material form or substance; unreal
lacking in substance or character
devoid of significance or force
as if echoing in a hollow space

hollow (verb)	unsubstantial (verb)
remove the interior of
remove the inner part or the core of