hollow vs natural depression

hollow and natural depression both are nouns.

Word	Noun	Adjective	Verb	Adverb
hollow	Yes	Yes	Yes	No
natural depression	Yes	No	No	No

As nouns, natural depression is a hypernym of hollow; that is, natural depression is a word with a broader meaning than hollow:

Other hypernyms of hollow include depression.

hollow (noun)	natural depression (noun)
a depression hollowed out of solid matter	a sunken or depressed geological formation
a small valley between mountains
a cavity or space in something

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

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