harbinger vs announce

harbinger is a noun but announce is not a noun.

Word	Noun	Adjective	Verb	Adverb
harbinger	Yes	No	Yes	No
announce	No	No	Yes	No

As verbs, harbinger and announce are synonyms defined as:

Other synonyms of harbinger include annunciate, foretell, herald.

harbinger (noun)	announce (noun)
something that precedes and indicates the approach of something or someone

harbinger (verb)	announce (verb)
foreshadow or presage	make known; make an announcement
	foreshadow or presage
	announce publicly or officially
	give the names of