Final answer:
The condition characterized by soft and weak bones in children due to a lack of vitamin D is known as rickets. This vitamin is critical for the proper mineralization of bones and its deficiency can also result in osteomalacia and osteoporosis in adults.
Step-by-step explanation:
The condition of soft, weak bones in children caused by a deficiency of vitamin D is called rickets. Rickets is a disorder that leads to skeletal deformities due to poor mineralization of the bones, primarily because of insufficient vitamin D, which is necessary for the absorption of calcium and phosphate from the intestines. Without adequate vitamin D, children can have a malabsorption of calcium, resulting in improper bone development. Vitamin D deficiency can also affect adults, leading to osteomalacia, which is soft bones that tend to fracture easily. This deficiency in adults can contribute to osteoporosis, a condition characterized by weak and brittle bones that are prone to fractures. Therefore, maintaining sufficient levels of vitamin D is crucial for bone health in both children and adults.