The concept of irreversibility is central in several disciplines, from physics to biology and economics, as well as in many philosophical disputes. Yet, it is seldom clearly defined. In this article, it is argued that the thermodynamic framework with its concept of entropy – allegedly the hallmark of irreversibility – offers a formal framework for a thorough conceptualisation of irreversibility based on three (generic) parameters: (1) the openness of the systems and the possible interventions, (2) the (acceptable) equivalence of the (...) final state, and (3) the timeframe. Its usefulness for socio-ecological systems, and hence for sustainable development and sustainability science, will be shown by presenting how these generic parameters can be applied and interpreted in topics such as the precautionary principle, climate change mitigation and environmental aesthetics. (shrink)