In Jewish law, a posek (Hebrew: פוסק [poˈsek], pl. poskim, פוסקים‎ [posˈkim]) is a legal scholar who determines the application of halakha, the Jewish religious laws derived from the written and Oral Torah in cases of Jewish law where previous authorities are inconclusive, or in those situations where no clear halakhic precedent exists. The decision of a posek is known as a psak halakha ("ruling of law"; pl. piskei halakha) or simply a "psak". Piskei halakha are generally recorded in the responsa literature. Source: Wikipedia (en)