1) Boniness 2) Constriction 3) Dimension 4) Fineness 5) Leanness 6) Reedy quality 7) Restriction 8) Scrawniness 9) Skinniness 10) Slenderness 11) Slightness 12) Slimness 13) Tenuity 14) Tightness 1) Bonyness 2) Emaciation 3) Fineness 4) Fluidity 5) Fluidness 6) Gauntness 7) Leanness 8) Littleness 9) Narrowness 10) Neatness 11) Rarity 12) Runniness 13) Scrawniness 14) Skinniness 15) Slenderness 16) Slimness 17) Tenuity 18) Wateriness 19) Weakness 
• (n.) The quality or state of being thin (in any of the senses of the word).
Thin'ness noun The quality or state of being thin (in any of the senses of the word). 
[n] - relatively small dimension through an object as opposed to its length or width 2. [n] - a consistency of low viscosity