ostentation vs ostentatious

ostentation is a noun but ostentatious is not a noun.

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

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

ostentation (adjective)	ostentatious (adjective)
	intended to attract notice and impress others
	(of a display) tawdry or vulgar