A collection of cards (or a deck) is a set of n rectangular pieces, usually made of heavy coated paper or cardboard, that hold special varying markings on one side and a uniform, identical pattern on the other. The special markings make each card unique, with each marking representing something playable in a certain card game.

The most common cards for games is a 52-card deck represented by four specifically colored suits (spades and clubs in black, diamonds and hearts in red), with 13 cards of each suit numbered 1 through 10, followed by several face cards—jack (J), queen (Q), and king (K). Card “1” is usually an “ace”; card 11 is represented by a “jack,” 12 by a “queen,” and 13 by a “king.” The value of the ace often changes depending on the game. For example, it can either hold a value of 1 or 11 (in blackjack) or 14 (in bridge). Such cards are also used for many gambling games, such as poker and baccarat. Interestingly enough, the investigation of the probabilities of various outcomes in card games was one of the original motivations for the development of modern probability theory. (For more about probability, see “Applied Mathematics.”)