Functional disorder
In medicine a functional disorder refers to a disorder or disease where the primary abnormality is an an alteration to the body's physiological function (that is, the way that the body works) rather than an identifiable structural, biochemical or biomechanical cause. In general such disorders cannot be diagnosed in a traditional way as an inflammatory, or infectious, or structural abnormality that can be seen observed through clinical examination, x-ray, or laboratory analysis. 

In speech-language pathology, we refer to 'functional speech disorders', 'functional communication disorders', and 'functional voice disorders' in that same sense. 

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