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."[1]
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?"[2]
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.