world war vs war

world war and war both are nouns.

Word	Noun	Adjective	Verb	Adverb
world war	Yes	No	No	No
war	Yes	No	Yes	No

As nouns, war is a hypernym of world war; that is, war is a word with a broader meaning than world war:

Other hypernyms of world war include warfare.

world war (noun)	war (noun)
a war in which the major nations of the world are involved	the waging of armed conflict against an enemy
	a concerted campaign to end something that is injurious
	an active struggle between competing entities
	a legal state created by a declaration of war and ended by official declaration during which the international rules of war apply

world war (verb)	war (verb)
	make or wage war