<p>The word &quot;sustainability&quot; has been connected to everything from a certain kind of economic development to corporate promises about improved supply sourcing. But despite the apparent ubiquity of the term, the concept of sustainability has come to mean a number of specific things. In this accessible guide to the meanings of sustainability, Kent Portney describes the evolution of the idea and examines its application in a variety of contemporary contexts -- from economic growth and consumption to government policy and urban planning.</p><p>Portney takes as his starting point the 1987 definition by the World Commission on Environment and Development of sustainability as economic development activity that &quot;meets the needs of the present without compromising the ability of future generations to meet their own needs.&quot; At its heart, Portney explains, sustainability focuses on the use and depletion of natural resources. It is not the same as environmental protection or natural resource conservation; it is more about finding some sort of steady state so that the earth can support both human population and economic growth. </p><p>Portney looks at political opposition to the promotion of sustainability, which usually questions the need for sustainability or calls its costs unacceptable; collective and individual consumption of material goods and resources and to what extent they must be curtailed to achieve sustainability; the role of the private sector, and the co-opting of sustainability by corporations; government policy on sustainability at the international, national, and subnational levels; and how cities could become models for sustainability action. </p>