A one-party state, single-party state, one-party system, or single-party system is a type of state in which one political party has the right to form the government, usually based on the existing constitution. All other parties are either outlawed or allowed to take only a limited and controlled participation in elections. Sometimes the term de facto one-party state is used to describe a dominant-party system that, unlike the one-party state, allows (at least nominally) democratic multiparty elections, but the existing practices or balance of political power effectively prevent the opposition from winning the elections.