Formal thought disorder is a disorder of the form of thought rather than of content of thought that covers hallucinations and delusions. FTD unlike hallucinations and delusions, is an observable objective sign of psychosis. FTD is a common, and core symptom of a psychotic disorder and may be seen as a marker of its severity, and also as a predictor of prognosis. It reflects a cluster of cognitive, linguistic, and affective disturbances, that has generated research interest from the fields of cognitive neuroscience, neurolinguistics, and psychiatry.