zugot

…judicial body headed by the zugot—pairs of scholars—assumed Halakhic authority. There were five pairs in all, between c. 150 and 30 bce. The first of the zugot also introduced the Mishnaic style of transmitting the oral tradition.

…controversy dates to the pre-tannaitic zugot. Hillel and Shammai differed on significant issues, and, with the rise of their schools, Halakhic uniformity began to crumble. Halakha became a scholastic discipline that developed in academic rather than judicial settings, more and more issues remaining unresolved. Over 300 controversies between the schools…