refractivity vs bending

refractivity and bending both are nouns.

Word	Noun	Adjective	Verb	Adverb
refractivity	Yes	No	No	No
bending	Yes	No	No	No

As nouns, bending is a hypernym of refractivity; that is, bending is a word with a broader meaning than refractivity:

refractivity: the physical property of a medium as determined by its index of refraction
bending: the property of being bent or deflected

Other hypernyms of refractivity include deflection, deflexion.

refractivity (noun)	bending (noun)
the physical property of a medium as determined by its index of refraction	the act of bending something
	the property of being bent or deflected
	movement that causes the formation of a curve