A takfiri (Arabic: تكفيري‎ takfīrī) is a Muslim who accuses another Muslim (or an adherent of another Abrahamic faith) of apostasy. The accusation itself is called takfir, derived from the word kafir (infidel), and is described as when "one who is, or claims to be, a Muslim is declared impure." The act of accusing other Muslims of being takfiri has itself become a sectarian slur particularly since the outbreak of the Syrian Civil War in 2011, as when used by Shi'a groups such as Hezbollah to refer to a Salafi Sunni sect. In principle the only group authorised to declare a member of an Abrahamic...