The common term for the infectious disease caused by a lack of vitamin D is rickets. Primarily affecting children, rickets results in weakened and softened bones, leading to deformities such as bowed legs and a curved spine. Vitamin D plays a vital role in calcium absorption, which is essential for bone health. Rickets is often seen in children with insufficient exposure to sunlight or inadequate dietary intake of vitamin D, calcium, or phosphorus, highlighting the importance of nutrition and sunlight.