Nonunion refers to a medical condition where a broken bone fails to heal properly and does not unite as expected. This can occur after a fracture due to various factors, such as inadequate blood supply, infection, or improper alignment of the bone fragments. In some cases, nonunion may require additional treatment, such as surgery or the use of devices like bone stimulators to promote healing. It is important for patients to follow their doctor's recommendations and attend follow-up appointments to monitor the healing process and address any complications that may arise.