 In Orthodox, Haredi and Hasidic circles, the term "illui" is applied to males only, as women are not obligated in Torah study to the same degree that men are required to devote much of their early life to serious and intense Torah studies, also referred to as Torah learning.Most rosh yeshivas (heads of yeshivas) have been called "illuim" as have many Hasidic Rebbes.There are some Judaic mystical traditions that explain how and why "illuim" are different.