WikiCards
Play on iPhone nowFree in Safari. Add it to your Home Screen.Play
WikiCards · Card list · Science cards · Empty set
Uncommon card · Science
Empty set, an Uncommon card
In mathematics, the empty set or void set is the unique set having no elements, its size or cardinality is zero.
- Rarity
- Uncommon
- Domain
- Science
- ATK
- 61
- DEF
- 44
- Power
- 105
- Wikipedia reads a year
- 82,000
Power 105 (ATK + DEF): stronger than 60 % of WikiCards cards.
Empty set quiz: 3 questions
Three questions on the Empty set card, the way WikiCards duels ask them. Pick an answer, the facts are just below.
Find the missing word
Many possible ______ of sets are vacuously true for the empty set.
Answer
properties. Many possible properties of sets are vacuously true for the empty set. From the Empty set article on Wikipedia.
Which of these cards hits hardest (highest ATK)?
Answer
Equal Earth projection. Equal Earth projection 73 · Therapy 69 · Laws of thermodynamics 64 · Empty set 61 ATK in WikiCards.
Which of these Wikipedia articles is read the most in a year?
Answer
Equal Earth projection. Equal Earth projection 560,000 · Laws of thermodynamics 270,000 · Empty set 82,000 · Arrowhead 57,000 Wikipedia reads over a year.
In a duel, each round asks a question like these about the opposing card, with 15 seconds to answer.
The facts on the card
The card carries these facts from its Wikipedia article.
- Some axiomatic set theories ensure that the empty set exists by including an axiom of empty set, while in other theories, its existence can be deduced.
- Many possible properties of sets are vacuously true for the empty set.
- Any set other than the empty set is called non-empty.
Why it is Uncommon
Rarity in WikiCards follows a year of Wikipedia page views: the most read articles become Epic and Legendary cards. The Empty set article was read about 82,000 times in a year. ATK comes from the length of the article and DEF from its quality, so this card hits with 61 and blocks with 44: each hit it takes is cut by 18 %.
How to get Empty set
Open packs. Each pack holds five cards drawn from real Wikipedia articles, the rarest last, and the fifth card is always Rare or better. The odds are shown in the game. A free pack arrives every hour and two can wait, and the Coins you win in duels buy more packs.
More Science cards
Cards close in power
The cards just above and just below Empty set in the power ranking, all domains together.
- MSC World EuropaUncommon · History · ATK 58 DEF 47
- TherapyUncommon · Science · ATK 69 DEF 36
- Antipope John XXIIIUncommon · Society · ATK 61 DEF 44
- Flag of SardiniaUncommon · Society · ATK 64 DEF 41
- CapraUncommon · Nature · ATK 62 DEF 43
- Mount PeléeUncommon · Nature · ATK 65 DEF 40
Card lists
- Wikipedia quizNew questions every day
- All cards from A to ZEvery card, by name
- Science cards
- Legendary cards
- Tier listS and A tiers by power (ATK + DEF)
Credits
Text : Wikipedia, Empty set (revision), CC BY-SA 4.0. Photo : Hugo Férée, CC BY-SA 3.0, Wikimedia Commons.
