abruptness vs suddenness

abruptness and suddenness both are nouns.

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

As nouns, abruptness and suddenness are synonyms defined as:

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

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

abruptness (noun)	suddenness (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