Multi-party system
In political science, a multi-party system is a political system where more than two meaningfully distinct political parties regularly run for office and win offices (eg, membership in parliament) in elections. Multi-party systems tend to be more common in countries or jurisdictions (together, 'polities') which use proportional representation forms of election, compared to those that have implemented winner-take-all elections; this tendency is known as Duverger's law.