In the 21st century, the various terms are usually focused on a city's financial power and high technology infrastructure, with other factors becoming less relevant. The term megacity entered common use in the late 19th or early 20th century, with the earliest documented example being a publication by the University of Texas in 1904.

The term world city, meaning a city heavily involved in global trade, appeared in a May 1886 description of Liverpool, by The Illustrated London News British sociologist and geographer Patrick Geddes likewise used the term in 1915. Prior to that, various other terms were used to describe urban centers with approximate features. The term global city was popularized by sociologist Saskia Sassen in her 1991 book, The Global City: New York, London, Tokyo. Quintessential examples, based on most indices and research, include New York City, London, Paris, and Tokyo.

The criteria of a global city have varied over time and depending on the source common features include a high degree of urban development, a large population, the presence of major multinational companies, a significant and globalized financial sector, well-developed and internationally linked transportation infrastructure, local or national economic dominance, high quality educational and research institutions, and a globally influential output of ideas, innovations, or cultural products. The global city represents the most complex and significant hub within the international system, characterized by links binding it to other cities that have direct, tangible effects on global socioeconomic affairs. The concept originates from geography and urban studies, based on the thesis that globalization has created a hierarchy of strategic geographic locations with varying degrees of influence over finance, trade, and culture worldwide. New York City (top) and London (bottom) are the only two cities ranked Alpha ++ by the Globalization and World Cities Research Network.Ī global city, also known as a power city, world city, alpha city, or world center, is a city that serves as a primary node in the global economic network.

Best cities in the world global index