Sustainable urbanism is both the study of cities and the practices to build them , that focuses on promoting their long term viability by reducing consumption, waste and harmful impacts on people and place while enhancing the overall well-being of both people and place. Well-being includes the physical, ecological, economic, social, health and equity factors, among others, that comprise cities and their populations. In the context of contemporary urbanism, the term cities refers to several scales of human settlements from towns to cities, metropolises and mega-city regions that includes their peripheries exurbs. Sustainability is a key component to professional practice in urban planning and urban design along with its related disciplines landscape architecture, architecture, and civil and environmental engineering. Green urbanism and ecological urbanism are other common terms that are similar to sustainable urbanism, however they can be construed as focusing more on the natural environment and ecosystems and less on economic and social aspects. Also related to sustainable urbanism are the practices of land development called Sustainable development, which is the process of physically constructing sustainable buildings, as well as the practices of urban planning called smart growth or growth management, which denote the processes of planning, designing, and building urban settlements that are more sustainable than if they were not planned according to sustainability criteria and principles.