The ABC for Sustainable Cities aims to bring clarity on this. Rather than providing a single univocal definition of what is a “Sustainable City”, it brings together key elements of it by compiling terms and concepts from internationally recognised sources. In doing so, the ABC will contribute to a better understanding of city-level sustainable development, where new concepts, phrases, terms and expressions are developed and used across the world. By providing a reference easily accessible to technical and non-technical audience, moreover, the ABC helps developing a common language and fosters dialogue among stakeholders and sets the basis for cooperation.