union
noun
1.
the action of joining together or the fact of being joined together, especially in a political context.
"he was opposed to closer political or economic union with Europe"
synonyms:unification, uniting, joining, merging, merger, fusion, fusing, amalgamating, amalgamation, junction, coalition, combining, combination, consolidation, conjunction, confederation, federation, integration, synthesis, blend, blending, mixture, mingling, commingling;
informalmash-up
"the gardens are an example of the union of art and nature"
2.
a society or association formed by people with a common interest or purpose.