luminescence vs luminousness

luminescence and luminousness both are nouns.

Word	Noun	Adjective	Verb	Adverb
luminescence	Yes	No	No	No
luminousness	Yes	No	No	No

As nouns, luminousness is a hypernym of luminescence; that is, luminousness is a word with a broader meaning than luminescence:

Other hypernyms of luminescence include brightness, brightness level, light, luminance, luminosity.

luminescence (noun)	luminousness (noun)
light from nonthermal sources	the quality of being luminous; emitting or reflecting light
light not due to incandescence; occurs at low temperatures