arms vs instrumentality

arms and instrumentality both are nouns.

Word	Noun	Adjective	Verb	Adverb
arms	Yes	No	No	No
instrumentality	Yes	No	No	No

As nouns, instrumentality is a hypernym of arms; that is, instrumentality is a word with a broader meaning than arms:

arms: weapons considered collectively
instrumentality: an artifact (that is instrumental in accomplishing some end) for accomplishing some end

Other hypernyms of arms include instrumentation, means.

arms (noun)	instrumentality (noun)
weapons considered collectively	an artifact (that is instrumental in accomplishing some end) for accomplishing some end
the official symbols of a family, state, etc.	the quality of being instrumental for some purpose
	a subsidiary organ of government created for a special purpose