International audienceRisk is an ubiquituous entity in biomedical science. References to various risks are consequently abundant in medical data. Thus, a consistent ontology of risk is necessary. Indeed, applied ontologies are used to structure data in order to facilitate its sharing between different information systems. Applied ontologies can be used for medical care and medical research. We analyze different definitions of risk and we identify two general characteristics that risks share with dispositions. Thus, we suggest to define risk as a disposition whose realization would be undesirable event for an agent. This definition conciles the objective dimension and the subjective dimension of risks : dispositions (and thus risks) exist wh...