Patrick Geddes also used the term 'world city' later in 1915. The use of 'global city', as opposed to 'megacity', was popularised by sociologist Saskia Sassen in her 1991 work, The Global City: New York, London, Tokyo although the term 'world city', which refers to cities involved with large amounts of global business, dates to at least the May 1886 description of Liverpool, by The Illustrated London News. The most complex of these entities is the 'global city', whereby the linkages binding a city have a direct and tangible effect on global affairs through socio-economic means.

The concept comes from geography and urban studies, and the idea that globalisation can be understood as largely created, facilitated, and enacted in strategic geographic locales according to a hierarchy of importance to the operation of the global system of finance and trade. A global city, also called world city or sometimes alpha city or world centre, is a city generally considered to be an important node in the global economic system.

List of alpha global cities