Pot odds Pot odds is one of the most important concepts in poker strategy. Pot odds are defined as the ratio of the size of the pot (including the next potential bet) to the size of the next potential bet, from the point of view of the player about to make the bet. For example, if a player is facing a $5 raise by his opponent (and must therefore pay $5 to call the raise), and the total amount of money in the pot (including the uncalled raise) is $30, then he is facing 6-to-1 pot odds for the call. If he is contemplating raising another $5 (making his potential bet $10 and the pot $35 including the $10 bet), then he is facing 3.5-to-1 pot odds for the raise and offering his opponent 8-to-1 pot odds ($5 call to make a $40 pot).

A playing card is a typically hand-sized rectangular (in India, round) piece of heavy paper or thin plastic used for playing card games. A complete set of cards is a pack or deck. Playing cards are often used as props in magic tricks, as well as occult practices such as cartomancy, and a number of card games involve (or can be used to support) gambling. As a result, their use sometimes meets with disapproval from some religious groups (such as a minority of conservative Christians).

The origin of playing cards is obscure, but it is almost certain that they began in China after the invention of paper. Ancient Chinese "money cards" have four "suits": coins (or cash), strings of coins (which may have been misinterpreted as sticks from crude drawings), myriads of strings, and tens of myriads. These were represented by ideograms, with numerals of 2-9 in the first three suits and numerals 1-9 in the "tens of myriads". Wilkinson suggests in The Chinese origin of playing cards that the first cards may have been actual paper currency which were both the tools of gaming and the stakes being played for. The designs on modern Mahjong tiles and dominoes likely evolved from those earliest playing cards.

The Chinese word pái (?) is used to describe both paper cards and gaming tiles. An Indian origin for playing cards has been suggested by the resemblance of symbols on some early European decks to the ring, sword, cup, and baton classically depicted in the four hands of Indian statues. This is an area that still needs research. The time and manner of the introduction of cards into Europe are matters of dispute. The 38th canon of the council of Worcester (1240) is often quoted as evidence of cards having been known in England in the middle of the 13th century; but the games de rege et regina there mentioned are now thought to more likely have been chess. If cards were generally known in Europe as early as 1278, it is very remarkable that Petrarch, in his dialogue that treats gaming, never once mentions them.

Boccaccio, Chaucer and other writers of that time specifically refer to various games, but there is not a single passage in their works that can be fairly construed to refer to cards. Passages have been quoted from various works, of or relative to this period, but modern research leads to the supposition that the word rendered cards has often been mistranslated or interpolated.