weapon system vs weapon

weapon system and weapon both are nouns.

Word	Noun	Adjective	Verb	Adverb
weapon system	Yes	No	No	No
weapon	Yes	No	No	No

As nouns, weapon system and weapon are synonyms defined as:

weapon system and weapon: any instrument or instrumentality used in fighting or hunting

Other synonyms of weapon system include arm.

weapon system (noun)	weapon (noun)
any instrument or instrumentality used in fighting or hunting	any instrument or instrumentality used in fighting or hunting
	a means of persuading or arguing