workfellow vs co-worker

workfellow and co-worker both are nouns.

Word	Noun	Adjective	Verb	Adverb
workfellow	Yes	No	No	No
co-worker	Yes	No	No	No

As nouns, workfellow and co-worker are synonyms defined as:

Other synonyms of workfellow include colleague, fellow worker.

workfellow (noun)	co-worker (noun)
an associate that one works with	an associate that one works with