Plurality

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Plurality is the state of having multiple headmates collectively sharing a single body. A group of headmates is called a system. Plural experiences are extremely diverse. Systems may be spiritual in nature or secular, median or partitonary, small systems or ones with thousands of headmates.

Headmates should be treated like any other individual, and generally assumed to have their own unique personality. They usually have their own names, pronouns, aesthetic, and writing style. Referring to the system they belong to is often done using plural pronouns like we, us, them, they, although it is best to not assume.

Causes
Plurality has many causes. This can include:
 * Traumagenic systems, resulting from a traumatic event or post-traumatic stress.
 * Systems created through tulpamancy or other explicit acts.
 * Other causes, which can be grouped under the umbrella term endogenic.
 * Mixed-origin systems, which have been created from a combination of causes.

Related Terms
Multiplicity is a synonym of plurality, and are often used interchangeably. Plural is an umbrella term for all kinds of experiences as well — so much so that the wiki itself is named using it.singlet:

Singlet refers to someone who is not plural. Not to be confused with singletsona.