artillery vs heavy weapon

artillery and heavy weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
artillery	Yes	No	No	No
heavy weapon	Yes	No	No	No

As nouns, artillery and heavy weapon are synonyms defined as:

Other synonyms of artillery include gun, ordnance.

artillery (noun)	heavy weapon (noun)
large but transportable armament	large but transportable armament
a means of persuading or arguing
an army unit that uses big guns