Defence Against the Dark Arts, commonly shortened to D.A.D.A., is the class that teaches students defensive techniques to defend against the Dark Arts, and to be protected from Dark creatures.
The subject has an extraordinarily high turnover of staff members — no Defence Against the Dark Arts teacher has remained at Hogwarts for more than one school year. It is suggested that Voldemort cursed the position because his application for it was rejected. For this reason, we have a new professor. Professor Wormwort will ba taking over the Defence Against the Dark Arts classes.