dearest vs sweetheart

dearest and sweetheart both are nouns.

Word	Noun	Adjective	Verb	Adverb
dearest	Yes	No	No	No
sweetheart	Yes	Yes	No	No

As nouns, dearest and sweetheart are synonyms defined as:

Other synonyms of dearest include baby, beloved, darling, dear, dearie, deary, honey, love, sweetie.

dearest (noun)	sweetheart (noun)
a beloved person; used as terms of endearment	a person loved by another person
	a very attractive or seductive looking woman
	any well-liked individual
	a beloved person; used as terms of endearment

dearest (adjective)	sweetheart (adjective)
	privileged treatment of a favored person or corporation (sometimes unethically)