ostentatiousness vs ostentation

ostentatiousness and ostentation both are nouns.

Word	Noun	Adjective	Verb	Adverb
ostentatiousness	Yes	No	No	No
ostentation	Yes	No	No	No

As nouns, ostentatiousness and ostentation are synonyms defined as:

ostentatiousness and ostentation: lack of elegance as a consequence of being pompous and puffed up with vanity

Other synonyms of ostentatiousness include inflation, pomposity, pompousness, pretentiousness, puffiness, splashiness.

ostentatiousness (noun)	ostentation (noun)
lack of elegance as a consequence of being pompous and puffed up with vanity	pretentious or showy or vulgar display
	lack of elegance as a consequence of being pompous and puffed up with vanity
	a gaudy outward display