Sri Lanka is a democratic republic and a unitary state which is governed by a semi-presidential system, with a mixture of a presidential system and a parliamentary system. Sri Lanka is the oldest democracy in Asia. Most provisions of the constitution can be amended by a two-thirds majority in parliament. The amendment of certain basic features such as the clauses on language, religion, and reference to Sri Lanka as a unitary state require both a two-thirds majority and approval in a nationwide referendum.