also been theorized to be caused by centrally mediated sensitivity to pain, and furthermore they often occur together. Definitions and terminology Frequently, TMD has been treated as a single syndrome, but the prevailing modern view is that TMD is a cluster of related disorders with many common features. Indeed, some have suggested that, in the future, the term TMD may be discarded as the different causes are fully identified and separated into different conditions. Sometimes, "temporomandibular joint dysfunction" is described as the most common form of temporomandibular disorder, whereas many other sources use the term temporomandibular disorder synonymously, or instead of the term temporomandibular joint dysfunction. In turn, the term temporomandibular disorder is defined as "musculoskeletal disorders affecting the temporomandibular joints and their associated musculature. It is a collective term which represents a diverse group of pathologies involving the temporomandibular joint, the muscles of mastication, or both". Another definition of temporomandibular disorders is "a group of conditions with similar signs and symptoms that affect the temporomandibular joints, the muscles of mastication, or both." Temporomandibular disorder is a term that creates confusion since it refers to a group of similarly symptomatic conditions, whilst many sources use the term temporomandibular disorders as a vague description, rather than a specific syndrome, and refer to any condition which may affect the temporomandibular joints (see table). The temporomandibular joint is susceptible to a huge range of diseases, some rarer than others, and there is no implication that all of these will cause any symptoms or limitation in function at all. The preferred terms in medical publications is to an extent influenced by geographic location. For example, in the United Kingdom, the term pain dysfunction syndrome is in common use. In the United States, the term temporomandibular disorder is generally favored. The American Academy of Orofacial Pain uses temporomandibular disorder, whilst the National Institute of Dental and Craniofacial Research uses temporomandibular joint disorder. A more complete list of synonyms for this topic is extensive, with some being more commonly used than others. In addition to those already mentioned, examples include temporomandibular joint pain dysfunction syndrome, temporomandibular pain dysfunction syndrome, temporomandibular joint syndrome, temporomandibular dysfunction syndrome, temporomandibular dysfunction, temporomandibular disorder, temporomandibular syndrome, facial arthromyalgia, myofacial pain dysfunction syndrome, craniomandibular dysfunction (CMD), myofacial pain dysfunction, masticatory myalgia, mandibular dysfunction, and Costen's syndrome. The lack of standardization in terms is not restricted to medical papers. Notable internationally recognized sources