weightiness vs weighty

weightiness is a noun but weighty is not a noun.

Word	Noun	Adjective	Verb	Adverb
weightiness	Yes	No	No	No
weighty	No	Yes	No	No

weightiness (noun)	weighty (noun)
the property of being comparatively great in weight
the relative importance granted to something

weightiness (adjective)	weighty (adjective)
	having relatively great weight; heavy
	excessively fat
	weighing heavily on the spirit; causing anxiety or worry
	of great gravity or crucial import; requiring serious thought
	powerfully persuasive