Final answer:
Osteoporosis is a disease that causes a decrease in bone mass and leads to thinning and weakening of the bones. It is more common in older adults and can increase the risk of fractures.
Step-by-step explanation:
Osteoporosis is a disease characterized by a decrease in bone mass that results in a thinning and weakening of the bone. This occurs when the rate of bone resorption exceeds the rate of bone formation, which is common as the body ages. Osteoporosis is different from other bone diseases like Paget's disease because in Paget's disease, new bone is formed but in a haphazard manner. Osteoporosis can lead to an increased risk of fractures, particularly in older adults.