slightness vs thinness

slightness and thinness both are nouns.

Word	Noun	Adjective	Verb	Adverb
slightness	Yes	No	No	No
thinness	Yes	No	No	No

As nouns, thinness is a hypernym of slightness; that is, thinness is a word with a broader meaning than slightness:

Other hypernyms of slightness include leanness, spareness.

slightness (noun)	thinness (noun)
slenderness	the property of having little body fat
the property of an attractively thin person	relatively small dimension through an object as opposed to its length or width
the quality of being unimportant and petty or frivolous	a consistency of low viscosity
	the property of being very narrow or thin
	the property of being scanty or scattered; lacking denseness
	The property of lacking substance or strength.