DADA

Defence Against the Dark Arts, also known by its acronym D.A.D.A., is a class taught at Hogwarts School of Witchcraft and Wizardry that focuses on defensive techniques to block spells, charms, curses, hexes, and jinxes cast by other wizards and witches, counteract the Dark Arts, and to protect from dark magical beasts and creatures such as the boggart. Defence Against the Dark Arts is taught to Hogwarts students from the first year to the fifth, with the option of N.E.W.T. classes in the sixth and seventh years for students who qualify.
~Harrypotter.wikia.com