arms vs weapons system

arms and weapons system both are nouns.

Word	Noun	Adjective	Verb	Adverb
arms	Yes	No	No	No
weapons system	Yes	No	No	No

As nouns, arms and weapons system are synonyms defined as:

Other synonyms of arms include implements of war, munition, weaponry.

arms (noun)	weapons system (noun)
weapons considered collectively	weapons considered collectively
the official symbols of a family, state, etc.