This document discusses various oral habits including mouth breathing, nail biting, self-injurious habits, and bobby pin opening. It provides details on the definition, classification, etiology, clinical features, diagnosis, and treatment of mouth breathing. Nail biting is introduced as a common habit seen in adolescents and students due to insecurity and stress. Self-injurious habits are most often seen in mentally retarded or psychologically abnormal individuals and can include biting of body parts. Treatment focuses on addressing the underlying causes and protecting injured areas.