skinniness vs spareness

skinniness and spareness both are nouns.

Word	Noun	Adjective	Verb	Adverb
skinniness	Yes	No	No	No
spareness	Yes	No	No	No

As nouns, spareness is a hypernym of skinniness; that is, spareness is a word with a broader meaning than skinniness:

Other hypernyms of skinniness include leanness, thinness.

skinniness (noun)	spareness (noun)
the bodily property of lacking flesh	the property of being scanty or scattered; lacking denseness
	the property of having little body fat