reflectivity vs coefficient

reflectivity and coefficient both are nouns.

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

As nouns, coefficient is a hypernym of reflectivity; that is, coefficient is a word with a broader meaning than reflectivity:

reflectivity: the fraction of radiant energy that is reflected from a surface
coefficient: a constant number that serves as a measure of some property or characteristic

reflectivity (noun)	coefficient (noun)
the ability to reflect beams or rays	a constant number that serves as a measure of some property or characteristic
the capability of quiet thought or contemplation
the fraction of radiant energy that is reflected from a surface