The United States of America (commonly abbreviated to the United States, the U.S., the USA, America, and the States) is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to the east and Russia to the west, across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific. The country also possesses several territories in the Pacific and Caribbean.

At 3.79 million square miles (9.83 million km²) and with over 312 million people, the United States is the third or fourth largest country by total area, and the third largest by both land area and population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The U.S. economy is the world's largest national economy, with an estimated 2011 GDP of $15.1 trillion (22% of nominal global GDP and over 19% of global GDP at purchasing-power parity). Per capita income is the world's sixth-highest.

Kei Nishikori (錦織 圭, Nishikori Kei^?) (born 29 December 1989 in Matsue, Shimane, Japan) is a Japanese tennis player, currently ranked World No. 17 as of April 2, 2012. He began playing tennis at the age of five and qualified for his first ATP main draw event at the Countrywide Classic in Los Angeles, California at the age of 17.^{[citation needed]}

Nishikori won the 2004 title at the Riad 21 Tournament in Rabat, Morocco and was a quarterfinalist at the 2006 Junior French Open. He partnered with Emiliano Massa to win the 2006 Junior French Open. Nishikori won the 2007 Luxilon Cup held at the 2007 Sony Ericsson Open by defeating Michael McClune.

Nishikori qualified and won the title at the ITF Futures event in Mazatlán, Mexico. He began the year by receiving a wildcard to the Kyoto Challenger in Kyoto, Japan.

A finalist in two USTA Pro Circuit events, Nishikori lost to Donald Young in Little Rock, Arkansas and Alex Bogomolov, Jr. in Carson, California. He partnered with Donald Young to win the doubles title at Little Rock. He paired with triple-French Open champion Gustavo Kuerten at the Sony Ericsson Open in Miami, Florida, where they lost in the first round. Nishikori served as a hitting partner for Roger Federer at Wimbledon.