Use the adjective corrigible when you want to emphasize that something can be improved or corrected. You might argue that even a country's constitution is corrigible, or hope that your physics midterm is corrigible. A much more common word is incorrigible, which means hopeless or not fixable, but is most often used to describe someone's personality. The Latin corrigere, "to put straight or set right," is the root of both corrigible and incorrigible.