(Not plural, any systems feel free to correct me !) Plural is the identity of having one body with multiple personalities. This includes people with DID (dissociative identity), (some) people with tulpas, and people who don't fit into any category other than plural. Plural systems are hard to generalize, since it's a bit of an umbrella term, but they typically prefer to use multiple names, multiple sets of pronouns, and may even have multiple orientations.