This word is occurring more and more. Sustainability can invoke fundamental yet complex concepts. What is sustainability? The word is derived from the Latin sustinere (tenere, to hold; sus, up). Dictionaries provide many meanings for sustain, the main ones being to “maintain", "support", or "endure”.
The most frequently used professional definition states: “Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.” This comes from the 1987 report of the World Commission on Environment and Development (also known as the Brundtland Report), an early landmark in developing what sustainability is today.
At larger scales, sustainability refers to attaining and ensuring a long-term balance among complex social, economic, and environmental systems. The goal of between-generation transfer of our current quality of life is fundamental; this requires thinking about present resource consumption - in terms of future resource needs. There are dozens of examples: many involve the adoption of best management practices - routines that improve near-term efficiency and long-term production.
Sustainability jobs often focus on developing best practices to ensure long-term system resilience. The Sustainability FAQs link has much additional information on the types of jobs in sustainability. Check out Table 1 at the end of that link for several detailed job lists.
As it sounds, sustainability often involves interdisciplinary tasks driven by the unique details of many different positions in diverse fields:
What is sustainability to a mechanical or electrical engineer?
It could be engineering new renewable technologies or more efficient fossil fuel energy systems.
What is sustainability to a city engineer?
It could be the conversion of a city bus fleet to natural gas.
What is sustainability to an environmental scientist?
It could be working for an agency developing management plans for protected areas with scientists and fishermen.
What is sustainability to a tech businessman?
It could be a corporate partnership with a non-profit organization to map out and improve product supply chains from the orginal sources through post-consumption options.
What is sustainability to a construction manager or architect?
It could be designing and/or construction buildings to LEED certification standards.
The goal of improving system operations across generations is critical; this requires research skills to manage current resource uses with future needs in mind to determine what is sustainable and improve what is not. Therefore, expertise in the measurement and analysis of metrics and indicators is fundamental to advanced sustainability practices.
There are many other research and management titles and occupations, see Sustainability FAQs and other resources on this and other web sites.