The Constitution of India is the world's longest written constitution and supreme legal document, outlining the structure, powers, and duties of government, along with fundamental rights and duties, adopted on November 26, 1949, and effective from January 26, 1950. Drafted over nearly three years by a committee led by Dr. B.R. Ambedkar, it establishes a quasi-federal system, comprising over 448 articles in 25 parts and 12 schedules. 
Wikipedia +4
Wikipedia +4Key Features and Structure
- Preamble: Defines India as a sovereign, socialist, secular, democratic republic, focusing on justice, liberty, equality, and fraternity.
- Fundamental Rights & Duties: Part III guarantees six core rights (Articles 12-35), while Part IVA outlines 11 fundamental duties.
- Governance & Federalism: Structures the union and state governments, including parliamentary democracy, an independent judiciary, and the separation of powers in the 7th Schedule.
- Amendments & Flexibility: As a "living document," it has undergone over 100 amendments to adapt to changing needs.
Key sections include Articles on citizenship (Part II), Directive Principles (Part IV), emergency provisions (Part XVIII), and amendment procedures (Part XX). The 12 schedules provide details on topics such as state boundaries, recognized languages (8th Schedule), and anti-defection laws (10th Schedule).