- Probably the most common, or at least the most well known, splitting at the point of a severe trauma, or to compartmentalise a recurring trauma.
- Some members of a collective are specifically there to fill a particular function. Protectors are most commonly mentioned, but they can be as varied as "the one who goes to school" or "dealing with the Boss" or such. Sometimes functional splits are entire complex personalities in themselves that take on the role much as any singleton might. Sometimes they are fragments who only have the capacity to do that one job (but do it well).
- Past Lives
- Splits along past-life lines seem fairly common within the otherkin scene. Which makes sense, as if you need a functional split, drawing on prior experience of a similar role is natural. If those lives involved their own traumas, that can be a source of trauma splits (dying can frequently be traumatic).