Initially the United Nations used the term to describe cities of 8 million or more inhabitants, but now uses the threshold of 10 million. The term 'megacity' entered common use in the late 19th or early 20th centuries one of the earliest documented uses of the term was by the University of Texas in 1904. Some sources identify Tokyo's Greater Tokyo Area as the largest megacity in the world, while some others give the title to Guangzhou's Pearl River Delta. African megacities are present in Nigeria, Egypt, South Africa, and the DRC European megacities are present in Russia, France, the United Kingdom, and Turkey (also in Asia) megacities can be found in Latin America in the countries of Brazil, Mexico, Colombia, Peru, and Argentina. The other four countries with more than one megacity are Brazil, Japan, Pakistan, and the United States. About half these urban agglomerations are in China and India. The total number of megacities in the world varies between different sources: The world had 33 according to the UN (in 2018), 37 according to (in 2020), and 35 according to Demographia (in 2020). The terms conurbation, metropolis, and metroplex are also applied to the latter. Others list cities satisfying criteria of either 5 or 8 million and also having a population density of 2,000 per square kilometre. A University of Bonn report held that they are 'usually defined as metropolitan areas with a total population of 10 million or more people'. Precise definitions vary: the United Nations Department of Economic and Social Affairs in its 2018 'World Urbanization Prospects' report counted urban agglomerations having over 10 million inhabitants. A megacity is a very large city, typically with a population of more than 10 million people.

Kiwix mega