The United Nations uses three definitions for what constitutes a city, as not all cities in all jurisdictions are classified using the same criteria. Cities may be defined as the cities proper, the extent of their urban area, or their metropolitan regions. The largest city by population using the city proper definition, which is the area under the administrative boundaries of a local government, is Chongqing, China. The largest city by population using the metropolitan area definition, which is a loose term referring to urban area and its primary commuter areas, is Tokyo, Japan. The largest city by population using the urban area definition, which is a loose term referring to a contiguous area with a certain population density, is also Tokyo, Japan.