leanness vs sparsity

leanness and sparsity both are nouns.

Word	Noun	Adjective	Verb	Adverb
leanness	Yes	No	No	No
sparsity	Yes	No	No	No

As nouns, sparsity is a hyponym of leanness; that is, sparsity is a word with a more specific, narrower meaning than leanness:

Other hyponyms of leanness include wateriness, abstemiousness, spareness, sparseness, thinness, thinness.

leanness (noun)	sparsity (noun)
the property of having little body fat	the property of being scanty or scattered; lacking denseness
the quality of being meager