coefficient of reflection vs reflectivity

coefficient of reflection and reflectivity both are nouns.

Word	Noun	Adjective	Verb	Adverb
coefficient of reflection	Yes	No	No	No
reflectivity	Yes	No	No	No

As nouns, coefficient of reflection and reflectivity are synonyms defined as:

coefficient of reflection and reflectivity: the fraction of radiant energy that is reflected from a surface

Other synonyms of coefficient of reflection include reflectance, reflection factor.

coefficient of reflection (noun)	reflectivity (noun)
the fraction of radiant energy that is reflected from a surface	the ability to reflect beams or rays
	the capability of quiet thought or contemplation
	the fraction of radiant energy that is reflected from a surface