post doc vs bookman

post doc and bookman both are nouns.

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

As nouns, bookman is a hypernym of post doc; that is, bookman is a word with a broader meaning than post doc:

post doc: a scholar or researcher who is involved in academic study beyond the level of a doctoral degree
bookman: a learned person; someone who by long study has gained mastery in one or more disciplines

Other hypernyms of post doc include investigator, research worker, researcher, scholar, scholarly person.

post doc (noun)	bookman (noun)
a scholar or researcher who is involved in academic study beyond the level of a doctoral degree	a learned person; someone who by long study has gained mastery in one or more disciplines
a grant that funds postdoctoral study or research