Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
union [ˈjuːnjən] n (unification) объедине́ние; (also: trade union) профсою́з
cpd (activities, leader etc) профсою́зный
the Union (US) Соединённые Шта́ты mpl
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.