harbinger vs precursor

harbinger and precursor both are nouns.

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

As nouns, harbinger and precursor are synonyms defined as:

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

Other synonyms of harbinger include forerunner, herald, predecessor.

harbinger (noun)	precursor (noun)
something that precedes and indicates the approach of something or someone	something that precedes and indicates the approach of something or someone
	a person who goes before or announces the coming of another
	a substance from which another substance is formed (especially by a metabolic reaction)

harbinger (verb)	precursor (verb)
foreshadow or presage