What is a constitution? What is the importance of a constitution in functioning of a nation?

A Constitution is a body of fundamental principles according to which a state is constituted or governed. It is the document or set of documents that form the basic rules agreed upon by the people on how to govern themselves. 

Importance of a Constitution in functioning of a nation: 

1. For cooperation and coordination: Any society comprises of diverse group of people. This can lead to various disputes. The Constitution provides some basic rules which ensure minimal degree of coordination.  
2. For assurance to people: Constitution also provides for enforcement of these rules. This assures people that everyone will follow these basic rules. Eg Justiciable nature of Fundamental Rights in the Indian Constitution. 
3. In order to remove ambiguity about decision making powers – The Constitution states who gets to decide what the rules and laws will be. It also specifies how the decisions will be made. Eg The Indian Constitution has entrusted the Parliament to make decisions regarding laws. 
4. Constitution is required to put necessary and reasonable restrictions on the power of the government. Eg Fundamental Rights limit the powers of the state. 
5. In order to achieve its aspirations, a society needs an enabling framework which instructs the government to do certain positive things, this is provided by a constitution. Eg Directive Principles of State Policy in the Indian Constitution. 
6. To prevent discrimination and oppression of one section of society by others. This is necessary for social progress and unity. Eg South African Constitution attempts to put an end to racial discrimination. 
7. This ensures collective good of the society and enables individuals to lead a life of minimal dignity and respect. It is necessary to achieve the ideals of Liberty, Equality and Justice. 
8. It provides Institutional set up necessary for proper functioning of a democracy. Eg. Election Commission of India provided by the Indian Constitution. 
9. A Constitution empowers the people to hold their government accountable. Eg Through regular elections. 

The Constitution is a dynamic document which ensures stability, security and progress of a nation. It entails the aspirations of people. It is important for social progress as well as economic prosperity of a nation.