A legislature is a kind of deliberative assembly with the power to pass, amend, and repeal laws. The law created by a legislature is called legislation or statutory law. In addition to enacting laws, legislatures usually have exclusive authority to raise or lower taxes and adopt the budget and other money bills. Legislatures are known by many names, the most common being parliament and congress, although these terms also have more specific meanings. In parliamentary systems of government, the legislature is formally supreme and appoints a member from its house as the prime minister which acts as the executive. In a presidential system, according to the separation of powers doctrine, the legislature is considered an independent and coequal branch of government along with both the judiciary and the executive. The primary components of a legislature are one or more chambers or houses: assemblies that can debate and vote upon bills. A legislature with only one house is called unicameral. A bicameral legislature possesses two separate chambers, usually described as an upper house and a lower house, which often differ in duties, powers, and the methods used for the selection of members. Much rarer have been tricameral legislatures; the Massachusetts Governor's Council still exists, but the most recent national example existed in the waning years of caucasian-minority rule in South Africa. I most parliamentary systems, the lower house is the more powerful house while the upper house is merely a chamber of advice or review. However, in presidential systems, the powers of the two houses are often similar or equal. In federations, it is typical for the upper house to represent the component states; the same applies to the supranational legislature of the European Union. For this purpose, the upper house may either contain the delegates of state governments, as is the case in the European Union and in Germany and was the case in the United States before 1913, or be elected according to a formula that grants equal representation to states with smaller populations, as is the case in Australia and the contemporary United States. Because members of legislatures usually sit together in a specific room to deliberate, seats in that room may be assigned exclusively to members of the legislature. In parliamentary language, the term seat is sometimes used to mean that someone is a member of a legislature. For example, saying that a legislature has 100 "seats" means that there are 100 members of the legislature, and saying that someone is "contesting a seat" means they are trying to get elected as a member of the legislature. By extension, the term seat is often used in less formal contexts to refer to an electoral district itself, as for example in the phrases "safe seat" and "marginal seat".