bipolar vs manic depressive illness

bipolar is not a noun while manic depressive illness is a noun.

Word	Noun	Adjective	Verb	Adverb
bipolar	No	Yes	No	No
manic depressive illness	Yes	No	No	No

bipolar (noun)	manic depressive illness (noun)
	a mental disorder characterized by episodes of mania and depression

bipolar (adjective)	manic depressive illness (adjective)
having two poles
of, pertaining to, or occurring in both polar regions
of or relating to manic depressive illness