Tokyo (東京, Tōkyō?), formally Tokyo Metropolis (東京都, Tōkyō-to?), is one of the 47 prefectures of Japan and, unique among the prefectures, provides certain municipal services characteristic of a city, as defined by Japanese law.Because it is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family, Tokyo is the de facto capital of Japan. (The name of Tokyo means "eastern capital" in Japanese).Tokyo is the most populous prefecture and city in the country. The twenty-three special wards of Tokyo, although each administratively a city in its own right, constitute the area informally considered as the "city of Tokyo" and are collectively one of the largest cities in the world with a total population of over 8 million people. The total population of the prefecture exceeds 12 million.The Greater Tokyo Area, centered on Tokyo but also including Chiba, Kanagawa, and Saitama, is the most populous metropolitan area in the world with a population of over 35 million people. It has been the world's most populous urban area since between 1965 and 1970, and despite Japan's overall declining population, is still growing.Tokyo has the largest metropolitan gross domestic product in the world for a city, and it held the title of the world's most expensive city for over a decade from 1992 through 2005.Tokyo is a major global city and megacity. The name "Tokyo" refers variously to Tokyo Metropolis (the prefecture) as a whole, or only to the main urban mass under its jurisdiction (thus excluding west Tama and Izu and Ogasawara Islands), or even the whole of Greater Tokyo Area, which includes Tokyo, Kanagawa, Saitama, Chiba, Gunma, Tochigi, Ibaraki, and Yamanashi prefectures, depending on context.This article uses the name to refer to Tokyo Metropolis unless otherwise stated.