thinness vs scrawniness

thinness and scrawniness both are nouns.

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

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

thinness (noun)	scrawniness (noun)
the property of having little body fat	the bodily property of lacking flesh
relatively small dimension through an object as opposed to its length or width	the property of being stunted and inferior in size or quality
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.