brilliance vs eclat

brilliance and eclat both are nouns.

Word	Noun	Adjective	Verb	Adverb
brilliance	Yes	No	No	No
eclat	Yes	No	No	No

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

brilliance (noun)	eclat (noun)
a light within the field of vision that is brighter than the brightness to which the eyes are adapted	brilliant or conspicuous success or effect
the quality of being magnificent or splendid or grand	ceremonial elegance and splendor
unusual mental ability	enthusiastic approval