A global city (also calle world city) is a city deemed to be an important node point in the global economic system. The concept comes from geography and urban studies and rests on 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. 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 terminology of "global city", as opposed to megacity, is thought to have been first coined by Saskia Sassen in reference to London, New York and Tokyo in her 1991 work The Global City.