Mussar מוסר
The teaching and movement of character work: not only knowing the law but changing oneself.
The word mussar appears already in Mishlei and means instruction or discipline. As a genre it dates from the rishonim: Duties of the Heart by Rabbeinu Bachya, Gates of Repentance by Rabbeinu Yona, Mesilat Yesharim by the Ramchal — books about inner obligations rather than outward acts.
As a movement it began in Lithuania in the mid-nineteenth century. Rabbi Yisrael Salanter saw the gap: people strict about kashrut and careless about honesty, who knew a tractate by heart and could not restrain anger. He proposed a method — reading short passages aloud, in a melody, at dusk, and examining one's own conduct.
Yeshivot resisted at first, holding that mussar took time from Gemara. In time a mashgiach appeared in the Lithuanian yeshivot — a mentor responsible for the person rather than the learning.