insane asylum vs mental institution

insane asylum and mental institution both are nouns.

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

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

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

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

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