heart-to-heart vs candid

heart-to-heart is a noun but candid is not a noun.

Word	Noun	Adjective	Verb	Adverb
heart-to-heart	Yes	Yes	No	No
candid	No	Yes	No	No

As adjectives, heart-to-heart and candid are synonyms defined as:

heart-to-heart and candid: openly straightforward and direct without reserve or secretiveness

Other synonyms of heart-to-heart include open.

heart-to-heart (noun)	candid (noun)
an intimate talk in private

heart-to-heart (adjective)	candid (adjective)
openly straightforward and direct without reserve or secretiveness	characterized by directness in manner or speech; without subtlety or evasion
	openly straightforward and direct without reserve or secretiveness
	informal or natural; especially caught off guard or unprepared