mental hospital vs insane asylum

mental hospital and insane asylum both are nouns.

Word	Noun	Adjective	Verb	Adverb
mental hospital	Yes	No	No	No
insane asylum	Yes	No	No	No

As nouns, mental hospital and insane asylum are synonyms defined as:

mental hospital and insane asylum: a hospital for mentally incompetent or unbalanced person

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

mental hospital (noun)	insane asylum (noun)
a hospital for mentally incompetent or unbalanced person	a hospital for mentally incompetent or unbalanced person