union
US /ˈjuː.njən/
UK /ˈjuː.njən/

1.
the action or fact of joining or being joined, especially in a political context.
:
•
The states formed a union to strengthen their defense.
•
The European Union promotes economic and political cooperation.
2.
a society or association organized for a common purpose, especially a trade union.
:
•
He joined the workers' union to fight for better wages.
•
The teachers' union is negotiating with the school board.