Urbanization refers to the process of a significant increase in the proportion of the population of a country or region living in urban areas (cities or towns). It involves the growth of urban areas in terms of both population and physical size, as well as the expansion of urban land use into surrounding rural areas. This can be due to various factors such as industrialization, rural-urban migration, and natural population growth. Option A "growth of towns, especially in terms of human population and physical size" accurately describes urbanization.