The aim of the current research series is to examine the definitions of the concept ‘risk’ and analyze the concepts used in the definitions of ‘risk’ in the sources of these definitions in order to perform the ontological analysis of the concept of ‘risk’. Ontological and epistemological analysis of the concepts in the definition of the concept ‘risk’ was used to answer the question what ‘risk’ means in project management. This investigation represents a part of the research series where the ontological, epistemological and methodological analysis of project risk is performed with the aim to improve risk registers and risk management as a whole. In the previous studies the author analyzed the concept of ‘event’ that defines the content of the concept ‘risk’. The use of ‘event’ was analyzed in different sources to find out how the concept should be used. The ontological, epistemological and methodological analysis of the definitions of the concept ‘risk’ is the theoretical foundation for risk register creation because it is possible to create complete and understandable register for the participants of the project risk management process. The author believes that the conducted research helps establish confidence that ontological analysis is the method that together with the epistemological and methodological analysis provides opportunity to perform analysis of risk management sources aimed at improving risk management. The results of the study cannot be considered sufficient for deriving valid conclusions about project risk management and developing recommendations for improving risk management with regard to the content of the risk register. For valid conclusions and recommendations, a deeper research is needed which, first of all, would analyze a larger number of sources.