The United States of America, also referred to as the United States, U.S.A., U.S., US, America, or the States, is a federal republic of fifty states, mostly in central North America. The U.S. has three land borders, two with Canada and one with Mexico, and is otherwise bounded by the Pacific Ocean, the Bering Sea, the Arctic Ocean and the Atlantic Ocean. Of the 50 states, however, there are two, Alaska and Hawaii, which are neither contiguous with the other forty-eight nor with each other, and the U.S. has also a collection of districts, territories, and possessions around the world. Each of the fifty states has a high level of local autonomy according to the system of federalism.