extravagance vs lavishness

extravagance and lavishness both are nouns.

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

As nouns, extravagance and lavishness are synonyms defined as:

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

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