reflectance vs coefficient

reflectance and coefficient both are nouns.

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

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

reflectance: 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

reflectance (noun)	coefficient (noun)
the fraction of radiant energy that is reflected from a surface	a constant number that serves as a measure of some property or characteristic