lavishness vs extravagance

lavishness and extravagance both are nouns.

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

As nouns, lavishness and extravagance are synonyms defined as:

Other synonyms of lavishness include high life, highlife, prodigality.

lavishness (noun)	extravagance (noun)
the activity of excessive spending	the activity of excessive spending
the quality possessed by something that is excessively expensive	the trait of spending extravagantly
	the quality of exceeding the appropriate limits of decorum or probability or truth