This paper suggests a formalization of the "risk" concept as the object of knowledge of epidemiological science, in order to categorize linguistic, epistemological and methodological aspects of this concept, following upon former contributions of the authors. Firstly, the meanings of risk are analyzed from an etymological and semantic viewpoint, evaluating its use for the constitution of common social discourses. Secondly, the epidemiological concept of risk is focused in hermeneutical perspective, making explicit epistemological axes and conceptual elements for the construction of the epidemiological discourse. Thirdly, theoretical, methodological and political correlations among the object risk, concepts of health and critical theories of society are discussed, aiming at an evaluation of perspectives and challenges for future developments of the scientific field of epidemiology.