bending vs refractivity

bending and refractivity both are nouns.

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

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

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

Other hyponyms of bending include wind deflection, windage, refractiveness.

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