Science / Psychiatry / Derailment: A pattern of speech in which a persons ideas slip off one track onto another that is completely unrelated or only obliquely related. In moving from one sentence or clause to another, the person shifts the topic idiosyncratically from one frame of reference to another and things may be said in juxtaposition that lack a meaningful relationship. This disturbance occurs between clauses, in contrast to incoherence, in which the disturbance is within clauses. An occasional change of topic without warning or obvious connection does not constitute derailment.
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