publishing company vs publishing firm

publishing company and publishing firm both are nouns.

Word	Noun	Adjective	Verb	Adverb
publishing company	Yes	No	No	No
publishing firm	Yes	No	No	No

As nouns, publishing company and publishing firm are synonyms defined as:

publishing company and publishing firm: a firm in the publishing business

Other synonyms of publishing company include publisher, publishing house.

publishing company (noun)	publishing firm (noun)
a firm in the publishing business	a firm in the publishing business