桡骨, or the radius, is one of the two long bones in the forearm, the other being the ulna. It is located on the thumb side of the forearm and extends from the elbow to the wrist. The radius plays a crucial role in the movement of the wrist and forearm, allowing for actions such as rotation and lifting. The radius has a distinctive shape, with a rounded head at the top that fits into the humerus at the elbow joint. At the wrist, it connects with the carpal bones, facilitating hand movements. Understanding the structure and function of the radius is essential in fields like anatomy and medicine.