Sustainability a definition

When Lori Beck came she mentioned that we did not really have a definition of sustainability. Hopefully as the semster progress I will have a better understanding of this term.Here is one definition from Wikipedia.

Sustainability, in a broad sense, is the capacity to endure. In ecology, the word describes how biological systems remain diverse and productive over time. For humans it is the potential for long-term maintenance of wellbeing, which in turn depends on the wellbeing of the natural world and the responsible use of natural resources.

the full article is longer than this introductory paragraph 

Wiki link: http://en.wikipedia.org/wiki/Sustainability