Facet

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A facet is a less-differentiated headmate, most commonly seen in median systems. They may present as an "alternate personality", a holder of specific traits or emotions, or a "mask" layered over a central headmate (called a core, blanketself, or other names). Facets do not typically have amnesiac barriers, but having them is possible.

Related Terms
Median systems commonly label their headmates as facets, while OSDD-1a systems sometimes do as well.

Facets that blur the line between kin and introject can identify as a fableing or factional.

Fragment may overlap and even be considered a synonym, depending on personal definition, since both terms refer to less-differentiated headmates.