Key constitutional features: World's longest written constitution (395 articles, 12 schedules); Borrowed from multiple sources - basic structure from GoI Act 1935, fundamental rights from US, directive principles from Ireland, cabinet system from Britain; Unitary nature with federal characteristics; 'Union of States' rather than federation; Parliamentary system with responsible government; Single citizenship; Secular governance; Balanced sovereignty between Parliament and Judiciary; Independent integrated judiciary; Directive Principles for welfare state; Fundamental Rights (Articles 12-35); Fundamental Duties (Article 51-A); Universal Adult Franchise; Emergency provisions; Special provisions for minorities and marginalized sections.