Urbanization, urbanisation or urban drift is the physical growth of urban areas as a result of global change or the increasing proportion of the total population becomes concentrated in towns. The United Nations projected that half of the world's population would live in urban areas at the end of 2008.

Urbanization is closely linked to modernization, industrialization, and the sociological process of rationalization. Urbanization can describe a specific condition at a set time, i.e. the proportion of total population or area in cities or towns, or the term can describe the increase of this proportion over time. So the term urbanization can represent the level of urban relative to overall population, or it can represent the rate at which the urban proportion is increasing.

As more and more people leave villages and farms to live in cities, urban growth results. The rapid growth of cities like Chicago in the late 19th century and Mumbai a century later can be attributed largely to rural-urban migration. This kind of growth is especially commonplace in developing countries. This growth can also be attributed to new job opportunities.

Geoffrey Brian West (born 1940) is a British theoretical physicist, former president and distinguished professor of the Santa Fe Institute. He is one of the leading scientists working on a scientific model of cities. Among other thing his work states that with the doubling of a city's size services per capita will generally increase by 15%.

Geoffrey West was born in 1940 in Taunton, Somerset, a rural town in western England and moved to London when he was 13. He received a bachelor's degree in physics from Cambridge and pursued graduate studies at Stanford, California.

He eventually became a Stanford faculty member before he joined the particle theory group at New Mexico's Los Alamos National Laboratory. After Los Alamos, he became president of the Santa Fe Institute, where he works on biological issues (such the allometric law and other power laws in biology).

He has since been honored as one of Time magazine's Time 100. He is a member of the World Knowledge Dialogue Scientific Board.