Ashkenazi Jews (/ˌɑːʃkəˈnɑːzi, ˌæʃ-/ A(H)SH-kə-NAH-zee; also known as Ashkenazic Jews) Ashkenazis or Ashkenazim form a distinct subgroup of the Jewish diaspora that emerged in the Holy Roman Empire in the Early Middle Ages, originating from the Jewish communities who lived in the 10th century in the Rhineland valley and in neighbouring France before migrating eastward after the Crusades. Facing persecution in Western Europe, particularly following the Black Death in the 14th century, the bulk of the Ashkenazi Jews migrated to the Kingdom of Poland, at the encouragement of Casimir III the Great and his successors, making Poland the main centre of Ashkenazi Jewry until the Holocaust.
They traditionally follow the German rite synagogue ritual and speak Yiddish, an offshoot of Middle High German written in a variety of the Hebrew script, with significant Hebrew, Aramaic and Slavic influence. Hebrew, on the other hand, was primarily used as a literary and sacred language until its 20th-century revival as a common language in Israel. Ashkenazim adapted their traditions to Europe, and underwent a transformation in their interpretation of Judaism. In the late 18th and 19th centuries, Jews who remained in or returned to historical German lands experienced a cultural reorientation. Under the influence of the Haskalah and the struggle for emancipation, as well as the intellectual and cultural ferment in urban centres, some gradually abandoned Yiddish in favor of German and developed new forms of Jewish religious life and cultural identity. Throughout the centuries, Ashkenazim made significant contributions to Europe's philosophy, scholarship, literature, art, music, and science.