beloved vs sweetheart

beloved and sweetheart both are nouns.

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

As nouns, beloved and sweetheart are synonyms defined as:

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

beloved (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

beloved (adjective)	sweetheart (adjective)
dearly loved	privileged treatment of a favored person or corporation (sometimes unethically)