/ ˈjuːniən; NAmE / noun
1.
[ C ] = trade / labor union :
I've joined the union .
a union member
2.
[ C ] an association or a club for people or organizations with the same interest :
the Scottish Rugby Union
—see also students' union (2)
3.
[ C ] a group of states or countries that have the same central government or that agree to work together :
the former Soviet Union
the European Union
4.
Union [ sing. ] the US (used especially at the time of the Civil War) :
the Union and the Confederacy
the State of the Union address by the President
5.
[ U , sing. ] the act of joining two or more things together; the state of being joined together; the act of two people joining together :
a summit to discuss economic and monetary union
Northern Ireland's union with Britain
sexual union
6.
[ C ] ( old-fashioned ) a marriage :
Their union was blessed with six children.
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WORD ORIGIN
late Middle English : from Old French , or from ecclesiastical Latin unio(n-) unity, from Latin unus one.