Since the High Middle Ages the three Jewish centers of the mid-Rhine region, Mainz, Worms and Speyer have been known by the acronym ShUM, composed of the first letter of the city names in Hebrew - Shin (Shpira), Waw (Warmaisa), and Mem (Magenza). The aura of the ShUM communities and the importance of the scholars and houses of learning, as well as the diverse traditions that are connected with them, explains the singular status of the three communities for Ashkenazic Judaism.