suddenness vs hastiness

suddenness and hastiness both are nouns.

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

As nouns, hastiness is a hypernym of suddenness; that is, hastiness is a word with a broader meaning than suddenness:

Other hypernyms of suddenness include haste, hurriedness, hurry, precipitation.

suddenness (noun)	hastiness (noun)
the quality of happening with headlong haste or without warning	hasty impulsiveness
	overly eager speed (and possible carelessness)