What is Sustainability

I'm not quite sure what sustainability means, and more than that what sustainability means to me. I do think that the definition of sustainability would include the idea of being able to exist in harmony with others, including the environment. I also think it would include the idea of the ability to use everything within a cycle of use and reuse (just like we see in nature) and to use everything within a limit so that the environment and others are not negatively impacted by our decisions.