System - among many other things - refers to the collective of alter
s within one body inhabited by multiple people.
The context is almost always the highly stigmatized mental disorders D.I.D.
(Dissociative Identity Disorder) or O.S.D.D.
(Otherwise Specified Dissociative Disorder) which both share the defining symptom of multiple alternate states of conciousnesses, colloquially referred to as alter
s or "multiple personalities". These alter
s often have different memories, abilities, etc. and can be just as different and well-defined as any other people in the world.
System refers to the collective of alter
s within one body.