abruptness vs abrupt

abruptness is a noun but abrupt is not a noun.

Word	Noun	Adjective	Verb	Adverb
abruptness	Yes	No	No	No
abrupt	No	Yes	No	No

abruptness (noun)	abrupt (noun)
the quality of happening with headlong haste or without warning
the property possessed by a slope that is very steep
an abrupt discourteous manner

abruptness (adjective)	abrupt (adjective)
	surprisingly and unceremoniously brusque in manner
	marked by sudden changes in subject and sharp transitions
	dangerously steep
	exceedingly sudden and unexpected