Surgery, as defined by the American Medical Association, is the treatment of disease, injury, or other disorders by direct physical intervention, usually with instruments.

Surgery involves the cutting into the skin or other organ to accomplish restoring the body to a healthy state.

This may include further exploration of the condition for the purpose of diagnosis, taking a biopsy of a suspicious lump, or removing diseased tissues or organs.
In addition, it surgery may be conducted to remove an obstruction, reposition structures to their normal position, redirect channels, or transplant tissue or whole organs.
Surgery may be needed to implant mechanical or electronic devices; improve physical appearance; repair an area that has been injured or affected by trauma, overuse, or disease; restore proper function; or relieve pain

Many people in the U.S. face surgery every year, both elective (by choice) and in cases of emergency.

When facing surgery, patients should expect to go through four phases. First, surgical diagnosis is made after medical tests and evaluations reveal a condition requiring surgery. Second, the preoperative management phase begins from the time surgery is decided to the point when the patient is brought to the operating room.

Third, the intraoperative care phase lasts from the time the patient enters the operating room to when the patient goes to the recovery room. And fourth, the postoperative management phase lasts from entry to the recovery room until follow-up clinical evaluation.