This Glossary defines concepts and terms commonly used in evaluation and results-based management. It provides a shared understanding to support the design, management, monitoring and evaluation of interventions for sustainable development. As a reference document, it is helpful for those commissioning, managing, or conducting evaluations, as well as people involved in strategy or programme development, management and implementation. While originally developed for international development co-operation, the Glossary can be applied in any field of public policy and is also useful for civil society, academia, and other non-state actors. This second edition includes updated content, including new definitions for the widely used evaluation criteria – relevance, coherence, effectiveness, efficiency, impact and sustainability – endorsed by the OECD Development Assistance Committee in 2019. It also provides minor updates to the original text to reflect current good practice. As concepts and language are constantly evolving, the document will be revisited and updated in due course.