Nouns

(n)thinness, tenuity, slendernessrelatively small dimension through an object as opposed to its length or width“the tenuity of a hair”, “the thinness of a rope”
(n)rarity, tenuity, low densitya rarified quality“the tenuity of the upper atmosphere”
(n)feebleness, tenuitythe quality of lacking intensity or substance“a shrill yet sweet tenuity of voice” (Nathaniel Hawthorne)