oth research and child protection practice are still far away from having uniform definitions of violence against children. The different disciplines involved in the sectors of national child protection systems rely on separate discourses and terms; definitions are sometimes rather general or implicit, and operationalizations of important elements are rare. The various terms in use – child maltreatment, child abuse and neglect, child endangerment, children at risk, children in need, etc. – speak of the variety, not only of concepts, but also of practices. With respect to the latter, definitional issues are also issues of the scope and thresholds of intervention. This chapter provides an overview of major terms and definitional approaches to violence against children and identifies eminent differences between them. Findings from several studies on the Swiss child protection system, including the first multi-sectorial national survey on agency responses to child maltreatment, illustrate how professionals use definitions and the consequences of having multiple definitional concepts for documenting reported cases. We conclude by advocating for a consensus-based interdisciplinary process of developing shared definitions of violence against children.