The Federative Republic of Brazil is a union of twenty-seven Federative Units (, UF): twenty-six states () and one federal district (), where the federal capital, Brasília, is located. The states are generally based on historical, conventional borders which have developed over time. The Federal District is not formally a state, but shares some characteristics of a state as well as some of a municipality. The codes given below are defined in ISO 3166-2:BR.