This report is the first output of Work Package 1: Diagnosis of the MYRIAD-EU project: Handbook of Multi-hazard, Multi-Risk Definitions and Concepts. The aim of the task was to (i) acknowledge the differences and promote consistency in understanding across subsequent work packages in the MYRIAD-EU project, (ii) improve the accessibility of our work to a broad array of stakeholders and (iii) strengthen consensus across the hazard and risk community through a common understanding of multi-hazard, multi-risk terminology and concepts. The work encompassed a mixed-methods approach, including internal consultations and data-generating exercises; literature reviews; external stakeholder engagement; adopting and building on a rich existing body of established glossaries. 140 terms are included in the glossary, 102 related to multi-hazard, multi-risk, disaster risk management and an additional 38 due to their relevance to the project, acknowledging the need for a common understanding amongst an interdisciplinary project consortium. We also include extended definitions related to concepts particularly of relevance to this project deliverable, including ‘multi-hazard’, ‘hazard interrelationships’, ‘multi-risk’ and ‘direct and indirect loss and risk’. Underpinned by a literature review and internal consultation, we include a specific section on indicators, how these might be applied within a multi-hazard and multi-risk context, and how existing indicators could be adapted to consider multi-risk management. We emphasise that there are a number of established glossaries that the project (and risk community) should make use of to strengthen the impact of the work we do, noting in our literature review a tendency in papers and reports to define words afresh. We conclude the report with a selection of key observations, including terminology matters – for all aspects of disaster risk management, for example communication, data collection, measuring progress and reporting against Sendai Framework targets. At the same time, we discuss when is it helpful to include ‘multi-‘ as a prefix, questioning whether part of the paradigm shift needed to successfully address complex challenges facing an interconnected world is through inherently seeing vulnerability, exposure and disaster risk through the lens of multiple, interrelated hazards. We emphasise that there is likely to be an evolution of the terminology throughout the project lifetime as terms are emerge or shift as the project evolves. Finally, we propose a roadmap for developing and testing draft multi-risk indicators in MYRIAD-EU. The WP1 team would like to acknowledge all the contributions of the consortium on this task and the feedback from the External Advisory Board, in particular the chair of the board Virginia Murray, Head of Global Disaster Risk Reduction at the UK Health Security Agency, and the contribution of Jenty Kirsch-Wood, Head of Global Risk Management and Reporting at UNDRR, for her reflections on the findings of this work.