luminousness vs brightness

luminousness and brightness both are nouns.

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

As nouns, luminousness and brightness are synonyms defined as:

luminousness and brightness: the quality of being luminous; emitting or reflecting light

Other synonyms of luminousness include brightness level, light, luminance, luminosity.

luminousness (noun)	brightness (noun)
the quality of being luminous; emitting or reflecting light	the location of a visual perception along a continuum from black to white
	the quality of being luminous; emitting or reflecting light
	intelligence as manifested in being quick and witty