researcher vs post doc

researcher and post doc both are nouns.

Word	Noun	Adjective	Verb	Adverb
researcher	Yes	No	No	No
post doc	Yes	No	No	No

As nouns, post doc is a hyponym of researcher; that is, post doc is a word with a more specific, narrower meaning than researcher:

researcher: a scientist who devotes himself to doing research
post doc: a scholar or researcher who is involved in academic study beyond the level of a doctoral degree

Other hyponyms of researcher include experimenter, boffin, fieldworker, postdoc.

researcher (noun)	post doc (noun)
a scientist who devotes himself to doing research	a scholar or researcher who is involved in academic study beyond the level of a doctoral degree
	a grant that funds postdoctoral study or research