The delivery of substandard care or services by a doctor, dentist, accountant, lawyer, or other professional. Generally, malpractice occurs when a professional 1) fails to provide a patient or client with the quality of care that can reasonably be expected in the circumstances, and 2) the patient or client is harmed as a result.
The professional's error (including their action or inaction) may be a result of their negligence, ignorance (something a qualified professional should have known), or intentional wrongdoing. In the area of medical malpractice, a key aspect of the patient's case is establishing the medical standard of care that applied under the circumstances, and showing exactly how the doctor or other care provider fell short of that standard while treating the patient.
(See also: errors and omissions)