disaffirmation vs asseveration

disaffirmation and asseveration both are nouns.

Word	Noun	Adjective	Verb	Adverb
disaffirmation	Yes	No	No	No
asseveration	Yes	No	No	No

As nouns, asseveration is a hypernym of disaffirmation; that is, asseveration is a word with a broader meaning than disaffirmation:

disaffirmation: the act of asserting that something alleged is not true
asseveration: a declaration that is made emphatically (as if no supporting evidence were necessary)

Other hypernyms of disaffirmation include assertion, averment.

disaffirmation (noun)	asseveration (noun)
the act of asserting that something alleged is not true	a declaration that is made emphatically (as if no supporting evidence were necessary)