tournament vs World Cup

tournament and World Cup both are nouns.

Word	Noun	Adjective	Verb	Adverb
tournament	Yes	No	No	No
World Cup	Yes	No	No	No

As nouns, World Cup is a hyponym of tournament; that is, World Cup is a word with a more specific, narrower meaning than tournament:

tournament: a sporting competition in which contestants play a series of games to decide the winner
World Cup: a soccer tournament held every four years between national soccer teams to determine a world champion

Other hyponyms of tournament include elimination tournament, open, round robin.

tournament (noun)	World Cup (noun)
a sporting competition in which contestants play a series of games to decide the winner	a soccer tournament held every four years between national soccer teams to determine a world champion
a series of jousts between knights contesting for a prize