anti-Semitism, prejudice against JEWS. Before the 19th cent. anti-Semitism was largely religious, based on the belief that Jews were responsible for Jesus' crucifixion. It was expressed in the later Middle Ages by sporadic persecutions and expulsions (e.g., the expulsion of Jews from Spain in 1492), economic restrictions (e.g., the restriction of Jews to unpopular or taboo occupations), and personal restrictions (see GHETTO). After the Jews' emancipation during the ENLIGHTENMENT, religious and economic anti-Semitism was slowly replaced in the 19th cent. by racial prejudice, stemming from the idea of Jews as a distinct race. The cultural isolation of Orthodox Jews, rising NATIONALISM, pseudoscientific theories of Aryan racial superiority, and spurious charges of Jewish domination encouraged anti-Semitism (see POGROM). These beliefs, incorporated into Adolf Hitler's NATIONAL SOCIALISM, contributed to the extermination of 6 million Jews in the HOLOCAUST of World War II. Since the 1980s anti-Semitic nationalists have become more influential in Russia, Germany, and other European countries. In the U.S. anti-Semitism persists among some extreme right-wing groups and in the practice of excluding Jews from certain clubs, schools, and housing.