Median

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A median system has members who are not as distinct or separate from each other as in partitionary systems, and are sometimes dependent on a single individual and unable to exist without that central person. The dependence can be mutual in that there is no central individual. Median systems often consist of members who all identify as "aspects" or "facets" of one central identity, which may be a single member or may be a sort of average identity of the group. Despite being more fluid and similar, median systems can be just as diverse as partitionary systems.

Related Terms
Median systems do not fit into the boxes dissociative disorders have offered — they don't have the amnesia for OSDD-1a or the separateness for OSDD-1b, let alone DID — but they can still be disordered in some way relating to their median-ness. BPD & PTSD (or C-PTSD) are common diagnoses for traumagenic or otherwise disordered medians.

A median system closer to the singlet side of the spectrum is called a parasian system; in the middle, a mesosian; the plural side, a diversian. A webbed median system is one without a core, while an orbital median system has one. Additionally, for some median systems, the term facet is preferred over headmate or alter, creating new labels like polyfaceted, for example.

History
Originally, median systems were referred to as "midcontinuum". It was coined in 1997 by Vickis, describing an experience of not explicitly multiple but not a singlet either. Encompassing the "grey area" across the dissociative spectrum, it amassed a large community. However, there was some concern with framing dissociation and plurality as a simple straight line (and the assumption that dissociation & plurality were one in the same). In 2002, the term "median" was coined to replace it by Blackbirds on Pavilion Hall. It has stuck around since.