Definition.
Multiple personality, also known as dissociative identity, is generally understood as a pathological state, multiple personality is the traumatogenic, intensified version of the normal and predominantly healthy plural psyche. In cases of multiple personality, however, the level of dissociation is more marked, and more pronounced ‘walls’ exist between parts/alters.
An expanded reading about multiple personality can be found in the article Multiple personality: The complex psychology of dissociative identity disorder.