Hasid (Hebrew: חסיד, "pious"; plural "Hasidim", חסידים) is a Jewish honorific, frequently used as a term of exceptional respect in the Talmudic and early medieval periods. In classic Rabbinic literature it differs from "Tzadik"-"righteous", by instead denoting one who goes beyond the legal requirements of ritual and ethical Jewish observance in daily life. The literal meaning of "Hasid" derives from Chesed-"kindness", the outward expression of love for God and other people. This spiritual devotion motivates pious conduct beyond everyday limits. The devotional nature of its description lent itself to a few Jewish movements in history being known as "Hasidim". Two of these derived from the Jewish mystical tradition, as it could tend towards piety over legalism.
As a personal honorific, both "Hasid" and "Tzadik" could be applied independently to a same individual with both different qualities. The 18th-century Vilna Gaon, for instance, while the head of Rabbinic opposition to the new Jewish mystical movement that itself became known as "Hasidism", was renowned for his righteous life. His scholarship became popularly honored with the formal title of "Genius", while amongst the Hasidic movement's leadership, despite his fierce opposition, he was respectfully referred to as "The Gaon, the Hasid from Vilna".
In the aggregate, it may refer to members of any of the following Jewish movements: