brilliancy vs splendor

brilliancy and splendor both are nouns.

Word	Noun	Adjective	Verb	Adverb
brilliancy	Yes	No	No	No
splendor	Yes	No	No	No

As nouns, brilliancy and splendor are synonyms defined as:

Other synonyms of brilliancy include luster, lustre, splendour.

brilliancy (noun)	splendor (noun)
a quality that outshines the usual	a quality that outshines the usual
	the quality of being magnificent or splendid or grand