The Multiple System
There are social systems, computer systems, network systems, plumbing systems, school systems, and in the realm of psychology, there are multiple systems.
See also Analogies for Systems New.
The term "system" in multiplicity includes all internal entities and processes, fragments, people, guests (or "stowaways"), residents (or "crew"), walk-ins, internal landscape, internal landscape components, and perhaps even some of the spirit guides or protector spirits who are linked into the energetic and mental landscape framework of the multiple. At minimum, "the system" should be considered to be the entire whole of all residents, constructs, fragments, and the multiple's body. A multiple system may include any number of sub-systems i.e. entities within a multiple system who are themselves also multiple systems.
A system is a functional organization of anything, basically. People may belong to a family system. Circulatory system, digestive system… A system is an assembly of many discrete "components" coming together within a discrete domain. Properly functioning systems work towards goals within a larger system or its external environment. One defining trait of a system is that there is exchange, feedback, commerce, flow, interdependence, chains of cause and effect, etc. within the system, and that there is a permeable boundary between the system and its environment i.e. the system may affect its environment, and the environment may affect the system, and there is commerce and communication between the system and its environment.
A school system includes people — teachers, students, cleaning staff, guards, and librarians — the vehicles it owns, the school buildings and grounds, the heirarchy of school units within the whole, the organizational decision hierarchy, etc. There's a permeable boundary — the people in the system can come and go, information passes through the boundary of the school system and the area it is in. However, it is relatively clear when something passes between the external environment and the school system — when information makes it onto school grounds, when people leave the school grounds. So there is a discrete permeable boundary for a school system.
Multiples are incredibly complicated, and as in any external system, the internal system is interreliant and interconnected. No matter if you look at everyone as independent entities who all have external sources, there are still physical and chemical reactions to thoughts and feelings that are going to be effecting the brain that everyone shares. No matter how high the boundaries are internally between the residents, information is shared on some level, even if it's repressed.
The food the bodily systems intake affect the mental systems. The drugs, the medications, the liquids, the air, etc. All of this affects the mental systems.
This is a "systems" approach to looking at multiplicity. From a more subjective viewpoint, it is advantageous to look at oneself as a "group entity" rather than a bunch of individuals at odds with one another. Very similar to how a family sometimes thinks as a group rather than competing individuals within the "family system".
There's some resistance in some portions of the plural community, because "The System" without a proper noun or adjective before it is like "The Man" — it's "the way things are" or the surrounding system, or the psychiatric system, the world, the community at large. For example as in this YouTube video on Person-Centered vs. System-Centered care referred to in a mental health peer specialist training in NY. Using the word "system" to be synonymous with multiple or plural may encounter a lot of resistance at the corporate, treatment, or government level due to the inherent ambiguity when not further clarified.