radiancy vs lambency

radiancy and lambency both are nouns.

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

As nouns, lambency is a hyponym of radiancy; that is, lambency is a word with a more specific, narrower meaning than radiancy:

Other hyponyms of radiancy include gleam, gleaming, glow, luster, lustre, sheen, shininess, burnish, gloss, glossiness, polish.

radiancy (noun)	lambency (noun)
the quality of being bright and sending out rays of light	an appearance of reflected light