shininess vs radiancy

shininess and radiancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
shininess	Yes	No	No	No
radiancy	Yes	No	No	No

As nouns, radiancy is a hypernym of shininess; that is, radiancy is a word with a broader meaning than shininess:

shininess: the visual property of something that shines with reflected light
radiancy: the quality of being bright and sending out rays of light

Other hypernyms of shininess include effulgence, radiance, refulgence, refulgency, shine.

shininess (noun)	radiancy (noun)
the visual property of something that shines with reflected light	the quality of being bright and sending out rays of light