folie a deux vs mental disorder

folie a deux and mental disorder both are nouns.

Word	Noun	Adjective	Verb	Adverb
folie a deux	Yes	No	No	No
mental disorder	Yes	No	No	No

As nouns, mental disorder is a hypernym of folie a deux; that is, mental disorder is a word with a broader meaning than folie a deux:

folie a deux: the simultaneous occurrence of symptoms of a mental disorder (as delusions) in two persons who are closely related (as siblings or man and wife)
mental disorder: (psychiatry) a psychological disorder of thought or emotion; a more neutral term than mental illness

Other hypernyms of folie a deux include disturbance, folie, mental disturbance, psychological disorder.

folie a deux (noun)	mental disorder (noun)
the simultaneous occurrence of symptoms of a mental disorder (as delusions) in two persons who are closely related (as siblings or man and wife)	(psychiatry) a psychological disorder of thought or emotion; a more neutral term than mental illness