1) A condition caused by deficiency of vitamin D, especially in infancy and childhood, with disturbance of normal ossification. The disease is marked by bending and distortion of the bones under muscular action, by the formation of nodular enlargements on the ends and sides of the bones, by delayed closure of the fontanels, pain in the muscles, and sweating of the head. Vitamin D and sunlight together with an adequate diet are curative, provided that the parathyroid glands are functioning properly. (Dorland, 27th ed)

2) Disorder of calcium and phosphorus metabolism affecting bony structures, due to a variety of defects in vitamin D, calcium, and phosphorous homeostasis, including dietary deficiencies or malabsorption.