The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or informally as America, is a country primarily located in North America consisting of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. It is the world's third-largest country by both land and total area. It shares land borders with Canada to its north and with Mexico to its south and has maritime borders with the Bahamas, Cuba, Russia, and other nations. With a population of over 333 million, it is the most populous country in the Americas and the third-most populous in the world. The national capital of the United States is Washington, D.C., and its most populous city and principal financial center is New York City.
Economy
The United States is a highly developed country that has the highest median income of any polity in the world. Its economy accounts for approximately a quarter of global GDP and is the world's largest by GDP at market exchange rates. It is the world's largest importer and second-largest exporter, and possesses the largest amount of wealth of any country. The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, NATO, World Health Organization, and is a permanent member of the United Nations Security Council. It wields considerable global influence as the world's foremost political, cultural, economic, military, and scientific power.
Technology
The United States has been a leader in technological innovation since the late 19th century and scientific research since the mid-20th century. Methods for producing interchangeable parts and the establishment of a machine tool industry enabled the U.S. to have large-scale manufacturing of sewing machines, bicycles, and other items in the late 19th century. In the early 20th century, factory electrification, the introduction of the assembly line, and other labor-saving techniques created the system of mass production.In the 21st century, approximately two-thirds of research and development funding comes from the private sector.In 2022, the United States was the country with the second-highest number of published scientific papers. As of 2021, the U.S. ranked second by the number of patent applications, and third by trademark and industrial design applications. In 2021, the United States launched a total of 51 spaceflights. The U.S. had 2,944 active satellites in space in December 2021, the highest number of any country. In 2022, the United States ranked 2nd in the Global Innovation Index.
As of 2021, the United States receives approximately 79.1% of its energy from fossil fuels. In 2021, the largest source of the country's energy came from petroleum (36.1%), followed by natural gas (32.2%), coal (10.8%), renewable sources (12.5%), and nuclear power (8.4%).The United States constitutes less than 5% of the world's population, but consumes 17% of the world's energy. It accounts for about 25% of the world's petroleum consumption, while producing only 6% of the world's annual petroleum supply. The U.S. ranks as second-highest emitter of greenhouse gases, exceeded only by China.
Education
In the United States, higher education is an optional stage of formal learning following secondary education. It is also referred as post-secondary education, third-stage, third-level, or tertiary education. It is delivered at 4,360 degree-granting institutions, known as colleges or universities. These may be public or private universities, research universities, liberal arts colleges, community colleges, or for-profit colleges. US higher education is loosely regulated by the government and by several third-party organizations.
In 2022, about 16 million students—9.6 million women and 6.6 million men—enrolled in degree-granting colleges and universities in the US. Of the enrolled students, 45.8% enrolled in a four-year public institution, 27.8% in a four-year private institution, and 26.4% in a two-year public institution. College enrollment has declined every year since a peak in 2010–2011 and is projected to continue declining or be stagnant for the next two decades.
Strong research funding helped elite American universities dominate global rankings in the early 21st century, making them attractive to international students, professors and researchers. The US higher education system is also unique in its investment in highly competitive NCAA sports, particularly in American football and basketball, with large sports stadiums and arenas adorning its campuses.