suddenness vs abruptness

suddenness and abruptness both are nouns.

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

As nouns, suddenness and abruptness are synonyms defined as:

suddenness and abruptness: the quality of happening with headlong haste or without warning

Other synonyms of suddenness include precipitance, precipitancy, precipitateness, precipitousness.

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