The foundation for government functions in the U.S. is the Constitution, ratified in 1788. This document outlines the structure, powers, and limits of government while establishing the principles of democracy and republicanism. It creates a system of checks and balances through its separation of powers among the legislative, executive, and judicial branches. The Bill of Rights, comprising the first ten amendments, further guarantees individual liberties and rights. Together, these elements form the framework for governance and have served as a model for democratic systems around the world.