The government of the United States can be most appropriately classified as a representative democracy.
A democracy, by definition, is a form of government in which the citizens of the society come together to debate the issues of concern to the whole of the society and then vote to determine a course of action in response to the given issues. A direct democracy involves all citizens in gathering together to make the governmental decisions needed for the functioning of the government.
The United States government is based on citizens electing representatives who are given the authority to act on behalf of the citizens in making the decisions necessary for the governing of the country. Representatives in the House of Representatives and senators in the Senate are empowered by the voters of their respective states to travel to Washington, D.C. and do the work of the national government on their behalf.