Third World vs collection

Third World and collection both are nouns.

Word	Noun	Adjective	Verb	Adverb
Third World	Yes	No	No	No
collection	Yes	No	No	No

As nouns, collection is a hypernym of Third World; that is, collection is a word with a broader meaning than Third World:

Third World: underdeveloped and developing countries of Asia and Africa and Latin America collectively
collection: several things grouped together or considered as a whole

Other hypernyms of Third World include accumulation, aggregation, assemblage.

Third World (noun)	collection (noun)
underdeveloped and developing countries of Asia and Africa and Latin America collectively	the act of gathering something together
	a publication containing a variety of works
	request for a sum of money
	several things grouped together or considered as a whole