sevens vs cards

sevens and cards both are nouns.

Word	Noun	Adjective	Verb	Adverb
sevens	Yes	No	No	No
cards	Yes	No	No	No

As nouns, cards is a hypernym of sevens; that is, cards is a word with a broader meaning than sevens:

sevens: a card game in which you play your sevens and other cards in sequence in the same suit as the sevens; you win if you are the first to use all your cards
cards: a game played with playing cards

Other hypernyms of sevens include card game.

sevens (noun)	cards (noun)
a card game in which you play your sevens and other cards in sequence in the same suit as the sevens; you win if you are the first to use all your cards	a game played with playing cards