What is the meaning of unification?

noun

• An occurrence that involves the production of a union.
  • synonyms: fusion, merger
• The state of being joined or united or linked.
  • usage: "there is strength in union"
  • synonyms: union
• The act of making or becoming a single unit.
  • usage: "the union of opposing factions"; "he looked forward to the unification of his family for the holidays"
  • synonyms: union, uniting, conjugation, jointure