NATO vs world organization

NATO and world organization both are nouns.

Word	Noun	Adjective	Verb	Adverb
NATO	Yes	No	No	No
world organization	Yes	No	No	No

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

NATO: an international organization created in 1949 by the North Atlantic Treaty for purposes of collective security
world organization: an international alliance involving many different countries

NATO (noun)	world organization (noun)
an international organization created in 1949 by the North Atlantic Treaty for purposes of collective security	an international alliance involving many different countries