The Politics of India works within the framework of the country's constitution. India is a parliamentary Democratic Republic in which the President of India is the head of state and the Prime Minister of India is the head of government. It is based on the federal structure of government although the word is not used in the constitution itself. India follows the dual polity system, i.e. a double government (federal in nature) that consists of the central authority at the centre and states at the periphery. The constitution defines the organisational powers and limitations of both central and state governments, and it is well recognised, fluid (Preamble of the constitution being rigid and to dictate further amendments to the constitution) and considered supreme; i.e. the laws of the nation must conform to it.