Greek fire vs weapon system

Greek fire and weapon system both are nouns.

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

As nouns, weapon system is a hypernym of Greek fire; that is, weapon system is a word with a broader meaning than Greek fire:

Greek fire: a mixture used by Byzantine Greeks that was often shot at adversaries; catches fire when wetted
weapon system: any instrument or instrumentality used in fighting or hunting

Other hypernyms of Greek fire include arm, weapon, mixture.

Greek fire (noun)	weapon system (noun)
a mixture used by Byzantine Greeks that was often shot at adversaries; catches fire when wetted	any instrument or instrumentality used in fighting or hunting