An alternative word for "multiplicity" or "Dissociative Identity Disorder (DID)" is "Multiple Personality Disorder" (MPD). However, it's important to note that "Multiple Personality Disorder" is an older term and is no longer used in the current psychiatric diagnostic classification systems.
"Dissociative Identity Disorder" (DID) is the currently accepted term used in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) published by the American Psychiatric Association. It replaced the term "Multiple Personality Disorder" to better reflect the understanding of the condition and reduce stigma surrounding the diagnosis.
If you encounter the term "Multiple Personality Disorder" in older literature or media, it refers to the same condition as "Dissociative Identity Disorder." However, it's essential to use the updated and more accurate term "Dissociative Identity Disorder" in modern discussions and clinical contexts.