reflexion vs reflectivity

reflexion and reflectivity both are nouns.

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

As nouns, reflexion and reflectivity are synonyms defined as:

Other synonyms of reflexion include reflection.

reflexion (noun)	reflectivity (noun)
the image of something as reflected by a mirror (or other reflective material)	the ability to reflect beams or rays
the ability to reflect beams or rays	the capability of quiet thought or contemplation
a likeness in which left and right are reversed	the fraction of radiant energy that is reflected from a surface
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