A headspace (sometimes called a innerworld or otherworld), is a place that those in plural systems might go to if they are not controlling the body or are otherwise not present fully in this physical world. Headspaces can be as unique and varied as the systems who have them, and some do not possess them at all.

Headspaces can be constructed, or come into being independent of anyone's thoughts or wishes. They can be as large and as immersive as a virtual game, or as small and as average as a grassy meadow. While some systems may experience their headspace as being a fully lifelike and real world, others may experience their headspace as only a dream world or as part of their imagination. There are those that have no headspaces, and those that perceive their headspaces with other senses or with certain senses prioritized over others. 

Oftentimes there is a sort of reality to a headspace, with members of the system interacting with each other inside of them. There may be internal happenings that hold importance in a system's life, and may need to be acknowledged. Depending on the amount of system members present, only a few may make use of this space, while others may spend their whole lives in the headspace, rarely coming out to interact with others outside.