This chapter focuses exclusively on medieval Jewish civilization, from the fall of the Roman Empire to about 1492. It includes alphabetically organized entries, written by scholars from around the world, include biographies, countries, events, social history, and religious concepts. Isabel of Castile, sister of the indecisive and possibly degenerate Enrique IV, was secretly proclaimed queen by rebellious nobles and clerics in 1468, but she refused to use the title while her brother still lived. Upon his death she officially became ruler of Castile. The most significant historical event at the beginning of the medieval period was the beginning of the Muslim conquests in the sixth century, which divided the Jewish world into two cultural and religious spheres: Islam and Christianity, East and West. Folklore elements that existed in the generations prior to the medieval period continued to exist in the Jewish tradition shared by all the Jewish communities in the Middle Ages.