illumination vs illuminance

illumination and illuminance both are nouns.

Word	Noun	Adjective	Verb	Adverb
illumination	Yes	No	No	No
illuminance	Yes	No	No	No

As nouns, illumination and illuminance are synonyms defined as:

illumination (noun)	illuminance (noun)
painting or drawing included in a book (especially in illuminated medieval manuscripts)	the luminous flux incident on a unit area
the luminous flux incident on a unit area
an interpretation that removes obstacles to understanding
the degree of visibility of your environment
a condition of spiritual awareness; divine illumination