predecessor vs harbinger

predecessor and harbinger both are nouns.

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

As nouns, predecessor and harbinger are synonyms defined as:

predecessor and harbinger: something that precedes and indicates the approach of something or someone

Other synonyms of predecessor include forerunner, herald, precursor.

predecessor (noun)	harbinger (noun)
something that precedes and indicates the approach of something or someone	something that precedes and indicates the approach of something or someone
one who precedes you in time (as in holding a position or office)

predecessor (verb)	harbinger (verb)
	foreshadow or presage