Scoliosis is a medical condition in which a person's spine has a sideways curve. The curve is usually "S" or "C" shaped. In some the degree of curve is stable while in others it increases over time. Mild scoliosis does not typically cause problems while severe cases can interfere with breathing. Pain is typically not present. Scoliosis occurs in about 3% of people. It most commonly occurs between the ages of ten and twenty. Girls typically are more severely affected than boys. The term is from Ancient Greek: σκολίωσις skoliosis which means "a bending".