There are many definitions of sustainable development, including this landmark one which first appeared in the 1987 United Nations Brundtland Report: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”  The United Nations 2005 World Summit Outcome Document refers to the “interdependent and mutually reinforcing pillars” of sustainable development as economic development, social development, and environmental protection.

Sources: United Nations (1987) "Report of the World Commission on Environment and Development." General Assembly Resolution 42/187, 11 December 1987; World Health Organization (2005) 2005 World Summit Outcome Document.