excellency vs excellence

excellency and excellence both are nouns.

Word	Noun	Adjective	Verb	Adverb
excellency	Yes	No	No	No
excellence	Yes	No	No	No

As nouns, excellency and excellence are synonyms defined as:

excellency and excellence: an outstanding feature; something in which something or someone excels

excellency (noun)	excellence (noun)
an outstanding feature; something in which something or someone excels	the quality of excelling; possessing good qualities in high degree
	an outstanding feature; something in which something or someone excels