world war vs warfare

world war and warfare both are nouns.

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

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

Other hypernyms of world war include war.

world war (noun)	warfare (noun)
a war in which the major nations of the world are involved	the waging of armed conflict against an enemy
	an active struggle between competing entities