What is a Government?

It's a way for a society to determine how to organize itself collectively.

Definitions: 

- Britannica:

. . . the political system by which a country or community is administered and regulated. Most of the key words commonly used to describe governments—words such as monarchy, oligarchy, and democracy—are of Greek or Roman origin.

- Wikipedia:

. . . the system or group of people governing an organized community, generally a state. In the case of its broad associative definition, government normally consists of legislature, executive, and judiciary. Government is a means by which organizational policies are enforced, as well as a mechanism for determining policy. In many countries, the government has a kind of constitution, a statement of its governing principles and philosophy.

- National Geographic Society:

. . . a system of order for a nation, state, or another political unit. A government is responsible for creating and enforcing the rules of a society, defense, foreign affairs, the economy, and public services. While the responsibilities of all governments are similar, those duties are executed in different ways depending on the form of government. Some of the different types of government include a direct democracy, a representative democracy, socialism, communism, a monarchy, an oligarchy, and an autocracy.

- Legal Information Institute:

the body, entity, invested with the power to manage a political unit, organization or more often, a State. Government, from the Latin locution gubernare - means steer a ship/vessel - describes the governing authority in charge of running a State. That governing body is oftentimes constituted by officials, ministers forming an active agency invested with the executive power and responsible for the direction and supervision of public affairs.

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In a different vein: 

What is Civil Society?

- Britannica:

the dense network of groups, communities, networks, and ties that stand between the individual and the modern state.

- Brookings:

organizations that are not associated with government—including schools and universities, advocacy groups, professional associations, churches, and cultural institutions (business sometimes is covered by the term civil society and sometimes not). Civil society organizations play multiple roles. They are an important source of information for both citizens and government. They monitor government policies and actions and hold government accountable. They engage in advocacy and offer alternative policies for government, the private sector, and other institutions. They deliver services, especially to the poor and underserved. They defend citizen rights and work to change and uphold social norms and behaviors.