transmittance vs coefficient

transmittance and coefficient both are nouns.

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

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

transmittance: the fraction of radiant energy that passes through a substance
coefficient: a constant number that serves as a measure of some property or characteristic

transmittance (noun)	coefficient (noun)
the fraction of radiant energy that passes through a substance	a constant number that serves as a measure of some property or characteristic