Sonderbehandlung (German: [ˈzɔndɐbəˌhandlʊŋ], "special treatment") is any sort of preferential treatment, but is known primarily as a euphemism for mass murder used by Nazi functionaries and the SS, who commonly used the abbreviation S.B. in documentation. It first came to prominence during Action T4, where SS doctors killed mentally ill and disabled patients between 1939 and 1941, and was one of a number of nonspecific words the Nazis used to document mass murder and genocide. Another notable example was Sonderbehandlung 14f13.