Urbanization, urbanisation or urban drift is the physical growth of urban areas as a result of global change. The United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

 projected that half of the world's population would live in urban areas at the end of 2008.

Urbanization is closely linked to modernization
In the social sciences, modernization or modernisation refers to a model of an evolutionary transition from a 'pre-modern' or 'traditional' to a 'modern' society. The teleology of modernization is described in social evolutionism theories, existing as a template that has been generally followed by...

, industrialization, and the sociological process of rationalization
Rationalization (sociology)
Rationalization is a term used in sociology to refer to a process in which an increasing number of social actions become based on considerations of teleological efficiency or calculation rather than on motivations derived from morality, emotion, custom, or tradition...

Urbanization can describe a specific condition at a set time, i.e.