Abstract: In order to understand the urbanization process, to develop policies for urban areas and to manage the process, there is a primary need for defining city and analyzing urbanization dynamics. For this reason, it is important to analyze the process of urbanization in the world and in Turkey, and to understand the evolution of definitions developed for city in line with the progress in urbanization process. With more than 70% urban population, Turkey does not have a standard method agreed upon that meets current needs for defining and classifying cities. Besides, existing definitions are far from the level that contemporary definitions and methods reached. Thus, across the world, New definitions and classifications are developed that take basis the population density, economic activities and relationships beyond population size. In this regard, current studies done for defining city in Turkey should be upgraded by taking into account the developments and new methods in the world.