reflectivity vs reflexion

reflectivity and reflexion both are nouns.

Word	Noun	Adjective	Verb	Adverb
reflectivity	Yes	No	No	No
reflexion	Yes	No	No	No

As nouns, reflectivity and reflexion are synonyms defined as:

Other synonyms of reflectivity include reflection.

reflectivity (noun)	reflexion (noun)
the ability to reflect beams or rays	the image of something as reflected by a mirror (or other reflective material)
the capability of quiet thought or contemplation	the ability to reflect beams or rays
the fraction of radiant energy that is reflected from a surface	a likeness in which left and right are reversed
	a calm, lengthy, intent consideration
	a remark expressing careful consideration
	expression without words
	the phenomenon of a propagating wave (light or sound) being thrown back from a surface