the act of federating or uniting in a league.

the formation of a political unity, with a central government, by a number of separate states, each of which retains control of its own internal affairs.

a league or confederacy.

a federated body formed by a number of nations, states, societies, unions, etc., each retaining control of its own internal affairs.

noun

alliance , amalgamation , association , bunch , coalition , combination , confederacy , crew , crowd , entente , family , federacy , gang , league , mob , outfit , pool , ring , syndicate , syndication , tribe , union , anschluss , bloc , cartel , confederation , organization , club , congress , fellowship , fraternity , guild , order , society , sorority , consortion , partnership