In the present world of urban studies there are distinct classifications and ideas about cities.Generally, conceptual strategies to cities could be divided into two primary classes: “size” and “operational” approach. The prior strategy is focusing on how big the city is in terms of it’s inhabitants. The operational approach is mostly concerned with the purposes completed by thecity for their areas, states, continents or internationally (e.g. highly technical fiscal solutions, which can be significant for the world market). The expression “mega-city” is situated at the prior strategy whereas “world” and also “international city” are groups of the operational strategy.SIZE vs OPERATIONALThe prior strategy is essentially concerned about the definition of minimal sizes for classificationof cities. Back in 1986 the United Nations described mega-cities as towns that were anticipated to get up to eight million individuals by the year 2000. There’s not any authentic conceptual foundation for placing eight million mark as minimal size for mega-cities or as Gilbert puts it “this minimum size seems to have plucked from the air”. Other institutions and researchers have supported the eight million mark or preferred different amounts which range from four to ten million inhabitants as minimal size.The first writer to mention and specify world cities has been Patrick Geddes somewhere around 1915. More lately Peter Hall’s publication “The World Cities” by 1966 could be regarded as a beginning point for defining world cities concerning their multiple functions. Examples to get categorizations can be taken from Saskia Sassen’s “Global Cities” that are categorized in accordance with their global top role in accountancy, marketing, banking/finance and regulation or Peter Hall’s “World Cities”, that can be described based on for their national/international governmental ability, their national/international transaction, their significance in banking, finance, and education, media and law.IMBRICATION: SIZE & OPERATIONALFor many mega-cities population expansion is accompanied by raised wealth of this city’s market and also an augmented significance for the area. Hence scholars have expanded the notion of mega-cities from purely based on size to also surrounding its function compared to other domestic and also regional towns and altering functional connections (e.g. Rakodi 1997). Rakodi points out that cities are mostly places of financial market with connections to their hinterland as well as the worldwide market (Rakodi 1997:4) and consequently a definition by Size isn’t sufficient. Additional indicators need to be included also. After Rakodi’s call to get a bigger definition of mega-cities (e.g. such as economical indicators) it is evident that there’s an overlap between both the theories. Many very big cities execute globally, nationally or regionally important works, so they fall within both groups, based on operations and size. However, obviously it is no requirement that size suggests increased significance.