An academic field of study: The study of government and political systems is a recognized academic discipline.
An organised group of people that formulate policies: This describes how government functions, with organised groups (such as branches or departments) responsible for policy-making.
A process of making and enforcing laws: Government involves the creation and enforcement of laws to maintain order and regulate society.
An institution made up of people with common interests, however, refers to organisations or groups that might not be governmental but are focused on shared goals or interests, such as clubs, societies, or special interest groups. These are not necessarily involved in the formal processes of governance.