Core

(Namespace: plural glossary)

Type of term	Possible type of headmate
Synonyms or near-synonyms	Original, self
Antonyms or near-antonyms	Alter, facade, facet, fragment

The core of a system is the headmate who serves as the system's centerpiece. They are the one who feels the most like a personification of the entire system, or the most like who the system is “supposed” to be.

The core may be, but is not necessarily, the same headmate as the host and/or original. Many systems, perhaps even most systems, do not have cores, or have more than one core.

Controversy

“Core” is terminology originating from the therapeutic model of internal family systems, which was implicated in the Alsana Castlewood tragedy. For this reason, even some systems who have headmates who could be called cores still choose not to use this word.