What is a Constitution? - Indian Polity and Governance Notes | Study Polity and Constitution (Prelims) by IAS Masters - UPSC

A constitution provides the basis for governance in a country, which is essential to making sure that everyone’s interests and needs are addressed. It determines how laws are made, and details the process by which the government rules. 

State

The most commonly used definition of State is Max Weber's:
It describes the State as a political organization with a, centralized government that maintains a monopoly of the legitimate use of force within a certain territory. General categories of state institutions include administrative bureaucracies, legal systems, and military organizations.

• According to the Oxford English Dictionary, a state is "an organized political community under one government".
• States may be classified as sovereign if they are not dependent on, or subject to any other power or state. Other states are subject to external sovereignty or hegemony where ultimate sovereignty lies in another state. For example, a colony.

The State and Government

The concept of the state can be distinguished from the concept of government. That is, governments are the means through which state power is used. 

• State is served by a continuous succession of different governments. State uses the instrument of Government to enforce its powers in the discharge of its duties.
• Each successive government is composed of a specialized and privileged body of individuals, who monopolize political decision-making and are separated by status and organization from the population as a whole. 
• Their function is to enforce existing laws, legislate new ones, and arbitrate conflicts. In some societies, this group is often a self-perpetuating or hereditary class. In other societies, such as democracies, governments change on the basis of periodical elections.
• States can also be distinguished from the concept of a "nation". The nation may refer to a community of people who share a common history, culture, some times ethnicity, and so on.
• However, it can also refer to people who share a common territory and government.

The State and Civil Society

State is the political entity. Family is a private institution. All institutions that fall in between can be called civil society.