Etiology, in the broadest sense, is the study of causation. Its most common use is in medicine, where it refers to the underlying cause of disease; Medical Subject Headings describes it as covering "causative agents including microorganisms and includes environmental and social factors and personal habits as contributing factors. It includes pathogenesis."
In medical usage, etiologic diagnosis is an intermediate point in restoring the best possible health to a patient. The first stage is recognizing the disturbance as a syndrome, or related group of symptoms, signs, and possibly the results of laboratory and imaging techniques. In simple terms, syndromic diagnosis asks "what is the problem to be solved?"
Given the anatomic and syndromic diagnosis, as well as the medical history and any indicated specialized examinations, a clinician determines the nature of the disorder, or pathologic diagnosis. The pathologic diagnosis deals with manifestation; determining causation is the result of the etiological diagnosis. Treatment deals with both correcting an abnormality that causes disease, as well as controlling unpleasant manifestations of the disease.