West Chester University
Sustainable development involves,
"...meeting the needs of the present without compromising the ability of future generations to meet their own needs." – (Earth Summit, Rio de Janeiro, 1992)
Another succinct definition is:
"the balance of people, profit, and the planet."
For those who like complete sentences:
"Organizing human activity so that society, its members and its economies are able to meet their needs and express their greatest potential in the present as well as the future."
You can learn more about the Earth Summit here at the Wikipedia entry for Earth Summit.
What is the difference between green and sustainability? This article from Ernest J. Yanarella, Richard S. Levine, and Robert W. Lancaster helps explain the differences.
This critical essay seeks to accomplish two things: draw out the differences between the green label and sustainability, and situate this debate within a hierarchical sustainability rubric that allows us to meaningfully offer gradations on the sustainability continuum. In so doing, we seek to illuminate the stakes involved in this conceptual debate and provide clarity about what these putative variations on sustainability imply for both theory and practice. In an age of mounting finite resource scarcities, rapid climate change, and continuing global population growth, combined with the growing clamor for Western-style economic development, the sustainability movement is not going to go away. Sadly, the meaning of sustainability and sustainable development remains highly contested and subject to ongoing and fierce dispute. This state of affairs is evidenced by the growing shift away from the language of sustainability and its variants to the increasingly popular, and easier to swallow, term green.
In design & architecture, sustainability has been enunciated in the setting of the Hannover Principles(click for full document).
William McDonough and Michael Braungart recently celebrated the 10th anniversary of their groundbreaking manifesto, The Hannover Principles: Design for Sustainability with the publication of a new, updated edition: From Principles to Practice