A constitution is a set of rules for government—often codified as a written document—that enumerates and limits the powers and functions of a political entity. These rules together make up, i.e. constitute, what the entity is. In the case of countries and autonomous regions of federal countries the term refers specifically to a constitution defining the fundamental political principles, and establishing the structure, procedures, powers and duties, of a government. By limiting the government's own reach, most constitutions guarantee certain rights to the people.