mental institution vs insane asylum

mental institution and insane asylum both are nouns.

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

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

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

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

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