psychopathology vs mental disorder

psychopathology and mental disorder both are nouns.

Word	Noun	Adjective	Verb	Adverb
psychopathology	Yes	No	No	No
mental disorder	Yes	No	No	No

psychopathology (noun)	mental disorder (noun)
the branch of medicine dealing with the diagnosis and treatment of mental disorders	(psychiatry) a psychological disorder of thought or emotion; a more neutral term than mental illness
the branch of psychology concerned with abnormal behavior