美利坚合众国(The United States of America)简称美国(U.S.A.)。位于北美洲中部(所属阿拉斯加在北美西北角，夏威夷在太平洋中部)。
北邻加拿大，西南接墨西哥，陆界长约9080公里；东濒大西洋，西临太平洋，东南临墨西哥湾，海岸线长约22 680公里。总面积9 372 614平方公里，仅次于俄罗斯、加拿大和中国，居世界第四位。
美国是一个移民国家，基本居民美利坚人主要由不同历史时期迁入的移民及其后裔组成，包括100多个民族成分，分属世界三大人种和各种混合类型。美国有“民族熔炉”之美誉，来自不同种族、不同国家的人民创造和发展了共同的文化。英语(美式英语)为通用语。有些民族讲本族语言，如部分印第安人讲印第安语，墨西哥人讲西班牙语，各国移民的后裔也有少数讲其祖先的语言。美国信奉宗教的人口约占全国人口的60%，主要信奉基督教、天主教、犹太教和东正教。基督教派别多达250多个。美国货币名称为美元，基本单位是元(dollar，符号＄)和分(cent，符号C)，1美元=100美分。
国名释义：
美利坚合众国(The United States of America)简称美国(U.S.A.)。美国因洲名而得名。在英语中，亚美利加和美利坚为同一词“America”，只是汉译不同，前者指全美洲，后者指美国。美国的绰号叫“山姆大叔”。传说1812年英美战争期间，美国纽约特罗伊城商人山姆·威尔逊在供应军队牛肉的桶上写有“u.s.”，表示这是美国的财产。这恰与他的昵称“山姆大叔”(“uncle sam”)的缩写(“u.s.”)相同，于是人们便戏称这些带有“u.s.”标记的物资都是“山姆大叔”的。后来，“山姆大叔”就逐渐成了美国的绰号。19世纪30年代，美国的漫画家又将“山姆大叔”画成一个头戴星条高帽、蓄着山羊胡须的白发瘦高老人。1961年美国国会通过决议，正式承认“山姆大叔”为美国的象征。
主要城市：
华盛顿市(哥伦比亚特区)、纽约市(纽约州)、芝加哥市(伊利诺伊州)、洛杉矶市(加利福尼亚州)、费城(宾夕法尼亚州)、休斯敦市(得克萨斯州)、底特律市(密歇根州)、达拉斯市得克萨斯州)、巴尔的摩市(马里兰州)、菲尼克斯市(亚利桑那州)、圣弗朗西斯科(即旧金山市，加利福尼亚州)、克利夫兰市(俄亥俄州)、波士顿市 (马萨诸塞州)、新奥尔良市(路易斯安那州)、西雅图市(华盛顿州)、丹佛市(科罗拉多州)、圣路易斯市(密苏里州)、明尼阿波利斯市(明尼苏达州)、火奴鲁鲁(即檀香山，夏威夷州)、布法罗市(纽约州)、盐湖城(犹他州)、朱诺市(阿拉斯加州)。
The United States of America - also referred to as the United States， the U.S.A.， the U.S.， America， the States， and (poetically) Columbia - is a democraticdemocratic adj.民主的， 民主主义的， 民主政体的， 平民的 constitutional federal republic of fifty states. Located primarily in central North America， the United States has land borders with Canada and Mexico， as well as territorialterritorial adj.领土的 water boundaries with Canada， Russia and the Bahamas. It is otherwise bounded by the Pacific Ocean， the Bering Sea， the Arctic Ocean， the Atlantic Ocean， the Gulf of Mexico， and the Caribbean Sea. Fortyeight of the states - often referred to as the Continental， Contiguous or Lower 48 - are located in a contiguous region between Canada and Mexico. Two of the fifty states， Alaska (an exclave) and Hawaii (an archipelago)， are not contiguouscontiguous adj.邻近的， 接近的， 毗邻的 with any of the other states. The United States also has a federal district - the District of Columbia - for its capital and a collection of overseas territories and possessions around the World. Each of the fifty states has a relatively high level of local autonomyautonomy n.自治 under the federal system.
The official founding date of the United States is July 4， 1776， the date the Second Continental Congress， representing the thirteen British colonies， adopted the Declaration of Independence. The structure of the United States was profoundly changed in 1788， however， when the states replaced the Articles of Confederation with the United States Constitution； often sources use the date each of the original thirteen states adopted the Constitution as the date that state “entered the Union” (became part of the United States). Since the mid twentieth century the United States has become the dominant global influence in contemporary economic， political， military， scientific， technological and cultural matters.
Physical Geography
As the world，s thirdlargest country (by total area)， the United States landscape varies greatly： temperate forestlandforestland n.林地 and rolling hills on the East coast， mangrove in Florida， the Great Plains in the center of the country， the Mississippi - Missouri river system， the Great Lakes which are shared with Canada， the Rocky Mountains west of the plains， deserts and temperate coastal zones west of the Rocky Mountains and temperate rain forests in the Pacific Northwest. Alaska，s tundra and the volcanic， tropical islands of Hawaii add to the geographic and climatic diversity.
The climate varies along with the landscape， from tropicaltropical adj.热带的， 热情的 in Hawaii and southern Florida to tundra in Alaska and atop some of the highest mountains. Most of the North and East experience a temperate continental climate， with warm summers and cold winters. Most of the American South experiences a subtropical humid climate with mild winters and long， hot， humid summers. Rainfall decreases markedly from the humid forests of the Eastern Great Plains to the semiaridsemiarid adj.雨量非常少的， 半干旱的 shortgrass prairies on the High Plains abutting the Rocky Mountains. Arid deserts， including the Mojave， extend through the lowlands and valleys of the American Southwest from westernmost Texas to California and northward throughout much of Nevada. Some parts of the American West， including California， have a Mediterranean climate. Rain forests line the windward mountains of the Pacific Northwest from Oregon to Alaska.
The United States has dozens of major cities， including several important global cities such as New York City， Los Angeles， and Chicago. The figures expressed below are for populations within city limits. A different ranking is evident when considering U.S. metroarea populations， although the top three would be unchanged.
Economy
The economy of the United States is organized primarily on a capitalist model， with some government regulation in many industries. There are also some social welfare programs like Social Security and unemployment benefits， Temporary Assistance to Needy Families (“welfare”)， the Earned Income Tax Credit， Medicare， and Medicaid. Such departuresdeparture n.启程， 出发， 离开 from a pure freemarket economy have generally increased since the late 1800s， but are less pronounced in the United States than in other industrialized countries.
The country has rich mineral resources， with extensive gold， oil， coal， and uranium deposits. Successful farm industries rank the country among the top producers of， among others， corn， wheat， sugar， and tobacco. The U.S. manufacturing sector produces， among other things， cars， airplanes， and electronics. The largest industry is now service， which employs roughly threequarters of U.S. residents.