Sustainability, in the broadest sense, is the ability to sustain a certain process or state at a certain rate or level. Sustainability ideas connect to ecological, social and economic points of view. Due to factors such as overpopulation, lack of education, inadequate financial circumstances and the actions of past generations, sustainability is problematic.

In the ecological context, sustainability is defined as the ability of an ecosystem to maintain ecological processes, functions, biodiversity and productivity into the future. In the social context, sustainability is expressed as meeting the needs of the present without compromising the ability of future generations to meet their own needs. In an economic context, a business is sustainable if it has adapted its practices for the use of renewable resources and is accountable for the environmental impacts of its activities.

To be sustainable, regardless of context, the Earth's resources must be used at a rate at which they can be replenished. There is now clear scientific evidence that humanity is living unsustainably, and that an effort is needed to keep human use of natural resources within sustainable limits. Due in part to its broad definition, sustainability has become a complex term that can be applied to almost every facet of life on Earth, particularly the many different levels of biological organization, such as; wetlands, prairies and forests, human organization, such as; eco-villages, eco-municipalities, sustainable cities, and human activities and disciplines, such as; sustainable agriculture, sustainable architecture and renewable energy.