forerunner vs harbinger

forerunner and harbinger both are nouns.

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

As nouns, forerunner and harbinger are synonyms defined as:

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

Other synonyms of forerunner include herald, precursor, predecessor.

forerunner (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
a person who goes before or announces the coming of another
anything that precedes something similar in time

forerunner (verb)	harbinger (verb)
	foreshadow or presage