The concept of “multimorbidity”, which refers to the simultaneous presence of multiple chronic diseases or conditions, is not understood in the same way by all physicians and other primary care professionals. There is no operational and consensual definition of multimorbidity per se. The theoretical basis of the concept is in great need of an in-depth analysis using different approaches including concept analysis, qualitative studies and case studies. The main goal is to harmonize the discourse and to propose a conceptualization that can be adopted by the entire clinical and research community. This step is necessary for the development of more appropriate interventions.