confidence vs diffident

confidence is a noun but diffident is not a noun.

Word	Noun	Adjective	Verb	Adverb
confidence	Yes	No	No	No
diffident	No	Yes	No	No

confidence (noun)	diffident (noun)
freedom from doubt; belief in yourself and your abilities
a secret that is confided or entrusted to another
a feeling of trust (in someone or something)
a state of confident hopefulness that events will be favorable
a trustful relationship

confidence (adjective)	diffident (adjective)
	lacking self-confidence
	showing modest reserve