dear vs sincere

dear is a noun but sincere is not a noun.

Word	Noun	Adjective	Verb	Adverb
dear	Yes	Yes	No	Yes
sincere	No	Yes	No	No

dear (noun)	sincere (noun)
a beloved person; used as terms of endearment
a sweet innocent mild-mannered person (especially a child)

dear (adjective)	sincere (adjective)
with or in a close or intimate relationship	open and genuine; not deceitful
having a high price	characterized by a firm and humorless belief in the validity of your opinions
dearly loved
sincerely earnest

dear (adverb)	sincere (adverb)
at a great cost
with affection