The condition resulting from a deficiency of vitamin D is known as rickets in children or osteomalacia in adults. Vitamin D is essential for calcium absorption, and a deficiency can lead to weakened bones and skeletal deformities. In children, rickets manifests as bone pain, delayed growth, and skeletal abnormalities, while adults may experience bone weakness and fractures. Ensuring adequate vitamin D levels through sun exposure, diet, or supplements is crucial for maintaining strong, healthy bones at all ages.