mental institution vs psychiatric hospital

mental institution and psychiatric hospital both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental institution	Yes	No	No	No
psychiatric hospital	Yes	No	No	No

As nouns, mental institution and psychiatric hospital are synonyms defined as:

mental institution and psychiatric hospital: a hospital for mentally incompetent or unbalanced person

Other synonyms of mental institution include asylum, insane asylum, institution, mental home, mental hospital.

mental institution (noun)	psychiatric hospital (noun)
a hospital for mentally incompetent or unbalanced person	a hospital for mentally incompetent or unbalanced person