There is no shortage of research on the changing nature of cities and the ways the increasing urbanisation is shaping modern life. Yet too often we fail to ask this simple, but fundamental question: What is a city? How do we determine what is, and what is not an urban reality. Of course we know that London is a bustling UK city, and sparsely populated farmland and moorland in Cumbria are not. In South Africa, we are aware that Gauteng province is urban, while Northern Cape province is not. Increasingly, however, geographical areas are emerging that do not so clearly fit inside or outside such a classification. As metropolitan areas evolve, as mid-sized cities reveal characteristics that are both urban and suburban, as cities and rural life are increasingly interconnected, defining just what we mean when we talk about cities becomes crucial.

Urbanisation is a dominant trend worldwide, affecting economies, societies, cultures and the environment. More than half the world’s population now lives in cities, and as much as two-thirds is expected to do so by 2050. The coming together of people, business and other activities in cities is a key process in the development and maturing of economies and societies. How urban systems function is crucial to future economic prosperity and a better quality of life for more than three billion people, and counting.

This chapter classifies and defines cities in South Africa from a migration vantage point. It first focuses on the differential urbanisation concept as a systemic framework that can explain how urban systems evolve and how the process determines the position and expected dynamism of individual cities within the urban hierarchy. Within this theoretical framework, the chapter reviews population redistribution patterns in South Africa since the mid- 1990s and compares them to population redistribution processes in the three largest urban agglomerations of South Africa. Finally, population redistribution movements in and around these core cities are used to explain: i) current morphological trends; ii) the relationship between the core cities and their surrounding cities; iii) the interpretation of functional and administrative space in terms of these trends. The chapter also reflects on the potential value to adapt the OECD methodology of functional urban areas to South Africa.

China’s rapid demographic transition is expected to lead to a contraction in the working-age population. Securing labour supply will depend on whether urbanisation can bring sufficient workers into urban areas. This chapter describes the urban system in China and examines how the urban population is defined. It then discusses the current level of urbanisation, analyses the regional spatial distribution of the urban population, and summarises general trends of urban population distribution. It uses this understanding to reflect on the potential for application of the OECD methodology of urban areas to China. Finally, the longer term urbanisation patterns in China are briefly discussed.