annulment vs breakup

annulment and breakup both are nouns.

Word	Noun	Adjective	Verb	Adverb
annulment	Yes	No	No	No
breakup	Yes	No	No	No

As nouns, breakup is a hypernym of annulment; that is, breakup is a word with a broader meaning than annulment:

annulment: (law) a formal termination (of a relationship or a judicial proceeding etc)
breakup: the termination or disintegration of a relationship (between persons or nations)

Other hypernyms of annulment include dissolution.

annulment (noun)	breakup (noun)
(law) a formal termination (of a relationship or a judicial proceeding etc)	the termination or disintegration of a relationship (between persons or nations)
the act of abrogating; an official or legal cancellation	coming apart
the state of being cancelled or annulled