stiffness vs rusticity

stiffness and rusticity both are nouns.

Word	Noun	Adjective	Verb	Adverb
stiffness	Yes	No	No	No
rusticity	Yes	No	No	No

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

stiffness: the inelegance of someone stiff and unrelaxed (as by embarrassment)
rusticity: the quality of being rustic or gauche

Other hyponyms of stiffness include woodenness, gaucherie.

stiffness (noun)	rusticity (noun)
the physical property of being inflexible and hard to bend	the quality of being rustic or gauche
the property of moving with pain or difficulty
the inelegance of someone stiff and unrelaxed (as by embarrassment)
excessive sternness
firm resoluteness in purpose or opinion or action