reunification vs uniting

reunification and uniting both are nouns.

Word	Noun	Adjective	Verb	Adverb
reunification	Yes	No	No	No
uniting	Yes	No	No	No

As nouns, uniting is a hypernym of reunification; that is, uniting is a word with a broader meaning than reunification:

Other hypernyms of reunification include conjugation, jointure, unification, union.

reunification (noun)	uniting (noun)
the act of coming together again	the act of making or becoming a single unit
	the combination of two or more commercial companies