Someone with an identity that goes beyond the traditional idea of being human. Examples include otherkin, therians, copinglinkers, synpaths, plurals, and other groups that either don't identify as human or have an unusual relationship with species and/or existence.

Members of a DID or OSDD-1 system; this is the psychiatric term for system members. Not used by systems that aren't disordered. For some nonexclusive terms that are used, see headmates

Blurring / Blending:
A state in which multiple system members are fronting, but it's difficult to tell who's who and where the lines between system members are. Some systems define blurring and blending separately, with blurring referring to a state where it is not known who is fronting, and blending referring to a state where multiple known people are fronting but it is difficult to tell them apart from one another. These states are jokingly referred to as "front soup" by some.

An internal presence that has some similarities with, but does not qualify as, a typical system member.

When more than one member of a system is aware of the world at the same time or is otherwise conscious.

When more than one member of a system is controlling the body at the same time.

DID and OSDD-1:
The medical diagnoses relating to some experiences of plurality. Dissociative Identity Disorder, or DID, is characterized by amnesia and distress in addition to plurality. Otherwise Specified Dissociative Disorder, or OSDD-1, is like DID but doesn't require amnesia or clear borders between system members. Not all systems have DID or OSDD.

Dormancy is a state in which a system member is unreachable by the rest of their system, does not front, and appears to be comatose or absent. This state may last for any length of time, even years, and it is not uncommon for system members to change in some way upon returning from dormancy.

How developed a system member is in personality, traits, and identity. A part with a more developed sense of self is more elaborated.

A member of a median system; is sometimes used synonymously with headmate.

The act of controlling the body. Being "in front" means being in active control.

Members of a system. Other common words include sysmates, parts, alters, others, headfolk, insiders, system members, crew, facets, etc.

Headspace / Inner World:
A place within a system's mind that the system's members live in, use as a communication tool, or otherwise interact with. Headspaces can be pre-existing, intentionally created, or a combination of the two. Not all systems have a headspace, and non-systems can have headspaces as well. It is possible to have multiple headspaces, sentient headspaces, nonvisual headspaces, and more.

The process of breaking down dissociative barriers. This can range from reducing amnesia between system members, to blending or merging them together to reduce the size of the system (usually called fusion). In the latter case, the integrated system members are still present, but as parts of a person rather than as separate people. The process of integrating all system members into a singular person is also known as final fusion, and it's not something every system will choose to pursue. Fusion in general is a sensitive topic for some systems, but it's not inherently a good or bad thing and should be left up to personal choice.

Internal Family Systems:
A mode of therapy that claims that all people are made of parts, that these parts interact with one another, and that these parts can be directly worked with to create change. It also claims that there is a central Self with certain qualities that ideally should lead the parts, but that this often does not happen because of outside pressures to behave a certain way, causing certain parts to be "foregrounded" and others to be "exiled." IFS is sometimes used to work with disordered systems, but it's more often used for singlets. Internal Family Systems is often shortened to IFS.

A system member based off or identifying as something from an outside source; for example, a system member that is based off Superman is an introject of that character. Types of introjects include fictives (fictional characters), factives (real-life people), and f*tives (doesn't fit neatly into fictive or factive). The person or media that an introject comes from is called their source.

A separate and self-contained area of the system that is typically difficult to reach from outside of it. One can think of layers as different floors of a building where the elevator doesn't work properly; these "floors" can be reached with effort, but are effectively separated in space and communications.

A word for children in a system. Can also refer to age regressors in general. While some use this word in a sexual sense pertaining to kink and ageplay, it's not usually used in this sense in plural circles, instead only referring to children and/or SFW age regression. Similar to syskids

A type of system where the members are not fully separated or distinct, but are still more separate than a singlet's ego states. Median experiences vary considerably and may or may not involve a shared identity.

A type of system where the members are fully separated and distinct.

An entity within a system's headspace that possesses little to no sentience, and who is not considered a member of the system. They may be puppets controlled by system members or the headspace, follow a script and be unable to deviate from it, and/or simply fill space to make headspace appear occupied.

A person who identifies with, but not as, a nonhuman entity or entities. This might feel like having a deep connection to that entity, feeling as though they are family, seeing yourself in them strongly, or otherwise strongly relating to them without feeling you are one inside. The species or entity an otherhearted person relates to is called their kithtype or hearttype. The words synpath and fictionhearted refer to this sort of connection with a fictional character or identity.

An umbrella term for any person that does not identify as human, instead involuntarily identifying as an animal, mythological species, fictional character, or other nonhuman entity. These species identities are called kintypes. Otherkin are fully aware that their body is human but nevertheless identify as something else. This can be psychological, spiritual, or both in explanation and varies from individual to individual. In recent years, the word has taken on the additional connotation of voluntarily chosen nonhuman or fictional identities in addition to involuntary identities, but this new meaning is the subject of considerable discourse. There are words for chosen identities that can be used without ruffling any feathers, such as copinglink, synpath, and otherlink. It's worth noting that nonhuman system members may not consider themselves to be otherkin.

Members of a system and/or subdivisions of oneself (depending on context). This word can be highly divisive and some people strongly dislike it; only call the members of a system "parts" if the system in question has asked you to.

The state of having more than one self in the same brain/body. There are many different experiences of plurality, but they are all united by being "more than one."

Someone who has only one person in their brain; a person that is not plural.

A persona or mask used by a system to pretend that they are a singlet, often for safety reasons.

A fictional character that someone has an abnormally strong connection to, often to the point of feeling that the character speaks to them or directly interacts with them. Some soulbonders share their body with their soulbonds in much the same manner as a plural group, while others do not share their body and merely have a strong internal connection to the character(s). More information on soulbonding can be found here.

The process of a new system member coming into existence as a result of stress or trauma.

A system within a system; when one's headmates have their own headmates. This can be experienced in many different ways, much like any system, and different subsystems within the same larger system may be experienced differently. Subsystems can be median or multiple

The act of changing who is in control of the body. May or may not be voluntary.

A word for children in a system.

The entire group of entities in one body.

An intentionally created member of a system; this word also includes servitors, which are non-sentient entities created to perform a task. When a thoughtform is sentient, it's more often called a tulpa or parogen.

The practice of intentionally creating a system member. The word itself is subject to some discourse regarding cultural appropriation, but the practice is quite different than the term by the same name. The term "parogenesis" was created to address these concerns but is not widely liked by those in this subset of the plural community.

A second-person pronoun that can be used to explicitly refer to all members of a plural group. Usage example: "I really like talking to you&."