extravagancy vs extravagance

extravagancy and extravagance both are nouns.

Word	Noun	Adjective	Verb	Adverb
extravagancy	Yes	No	No	No
extravagance	Yes	No	No	No

As nouns, extravagancy and extravagance are synonyms defined as:

extravagancy and extravagance: the quality of exceeding the appropriate limits of decorum or probability or truth

extravagancy (noun)	extravagance (noun)
the quality of exceeding the appropriate limits of decorum or probability or truth	the activity of excessive spending
	the trait of spending extravagantly
	the quality of exceeding the appropriate limits of decorum or probability or truth