harbinger vs forerunner

harbinger and forerunner both are nouns.

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

As nouns, harbinger and forerunner are synonyms defined as:

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

Other synonyms of harbinger include herald, precursor, predecessor.

harbinger (noun)	forerunner (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
	anything that precedes something similar in time

harbinger (verb)	forerunner (verb)
foreshadow or presage