stiffness vs inelasticity

stiffness and inelasticity both are nouns.

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

As nouns, inelasticity is a hypernym of stiffness; that is, inelasticity is a word with a broader meaning than stiffness:

stiffness (noun)	inelasticity (noun)
the physical property of being inflexible and hard to bend	the lack of elasticity
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