South Korea, officially known as the Republic of Korea (ROK; Hangeul: 대한민국; Daehan Minguk; ⓘ), is a country located in eastern Eurasia, constituting the southern part of the Korean Peninsula. The word "Korea" is derived from the Kingdom of Goryeo, also known as "Koryŏ". It shares land borders with North Korea to the north, and oversea borders with Japan to the east and China to the west. Roughly half of the country's 50 million people reside in the metropolitan area surrounding its capital, the Seoul Capital Area, which is the second largest in the world with over 25 million residents.