Social appropriateness is an important topic – both in the human-human interaction (HHI), and in the human-machine interaction (HMI) context. As sociosensitive and socioactive assistance systems advance, the question arises whether a machine’s behavior should include considerations regarding social appropriateness. However, the concept of social appropriateness is difficult to define, as it is determined by multiple aspects. Thus, to date, a unified perspective, encompassing and combining multidisciplinary findings, is missing. When translating results from HHI to HMI, it remains unclear whether (...) such insights into the dynamics of social appropriateness between humans may in fact apply to sociosensitive and socioactive assistance systems. To shed light on this matter, we propose the Five Factor Model of Social Appropriateness (FASA) which provides a multidisciplinary perspective on the notion of social appropriateness and its implementation into technical systems. Finally, we offer reflections on the applicability and ethics of the FASA Model, highlighting both strengths and limitations of the framework. (shrink)