extern vs doc

extern and doc both are nouns.

Word	Noun	Adjective	Verb	Adverb
extern	Yes	No	No	No
doc	Yes	No	No	No

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

extern: a nonresident doctor or medical student; connected with a hospital but not living there
doc: a licensed medical practitioner

Other hypernyms of extern include doctor, Dr., MD, medico, physician.

extern (noun)	doc (noun)
a nonresident doctor or medical student; connected with a hospital but not living there	a licensed medical practitioner