A single-party state, one-party state, one-party system or single-party system is a type of state in which a single political party forms 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 the election. Sometimes the term de facto single-party state is used to describe a dominant-party system that, unlike the single-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. Single-party states are often, but not always, considered to be totalitarian. Some single-party states are widely seen as authoritarian and not totalitarian.