weighty vs weightiness

weighty is not a noun while weightiness is a noun.

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

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

weighty (adjective)	weightiness (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