field gun vs artillery

field gun and artillery both are nouns.

Word	Noun	Adjective	Verb	Adverb
field gun	Yes	No	No	No
artillery	Yes	No	No	No

As nouns, artillery is a hypernym of field gun; that is, artillery is a word with a broader meaning than field gun:

field gun: movable artillery (other than antiaircraft) used by armies in the field (especially for direct support of front-line troops)
artillery: large but transportable armament

Other hypernyms of field gun include gun, heavy weapon, ordnance.

field gun (noun)	artillery (noun)
movable artillery (other than antiaircraft) used by armies in the field (especially for direct support of front-line troops)	large but transportable armament
	a means of persuading or arguing
	an army unit that uses big guns