opalescence vs brightness

opalescence and brightness both are nouns.

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

As nouns, brightness is a hypernym of opalescence; that is, brightness is a word with a broader meaning than opalescence:

opalescence: the visual property of something having a milky brightness and a play of colors from the surface
brightness: the location of a visual perception along a continuum from black to white

opalescence (noun)	brightness (noun)
the visual property of something having a milky brightness and a play of colors from the surface	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