Singapore is governed under the constitution of 1959 as amended. The country has a parliamentary form of government. The president, who is head of state, is popularly elected for a six-year term. The government is headed by the prime minister, who is appointed by the president. The unicameral legislature consists of the 84-seat Parliament, whose members are popularly elected for five-year terms; additional members may be appointed. The supreme court, the nation's highest judicial body, has seven members. The People's Action party (PAP) is the most important of Singapore's numerous political parties; it has been in power since 1959.