The Geonim in their " Responses " or " Questions and Answers " supplied authoritative interpretations of the Old Testament or of the Talmud, and regulated the application of the teaching of the past to the changed conditions under which their brethren now lived.
G Y Geonim, the heads of the schools of Sura and Pumbeditha in Babylonia.
Individual Geonim produced valuable works (of which later), but what is perhaps most important from the point of view of the development of Judaism is the literature of their Responsa or answers to questions, chiefly on halakhic matters, addressed to them from various countries.
Some of these were actual decisions of particular Geonim; others were an official summary of the discussion of the subject by the members of the School.
All these writers, however, are entirely eclipsed by the commanding personality of the most famous of the Geonim, Seadiah ben Joseph (q.v.) of Sura, often called al-Fayyumi (of the Fayum in Egypt), one of the greatest representatives of Jewish learning of all times, who died in 942.