Blackjack, also known as Twenty-one or Vingt-et-un (French: “twenty-one”), is the most widely played casino banking game in the world. Blackjack is a comparing card game between a player and dealer and played with one or more French decks of 52 cards.

The player is dealt an initial two card hand with the option of drawing cards to bring the total value to 21 or less without exceeding it, so that the dealer will lose by having a lesser hand than the player or by exceeding 21. Many rule variations of blackjack exist. Since the 1960s, blackjack has been a high profile target of advantage players, particularly card counters, who track the profile of cards yet to be dealt, and adapt their wager and playing strategy accordingly.

After receiving an initial two cards, the player has up to four standard options: “hit,” “stand,” “double down,” or “split”. Each option has a corresponding hand signal. Some games give the player a fifth option, “surrender”.

* Hit: Take another card from the dealer.

signal: (handheld) Scrape cards against table. (face up) Tap the table or wave hand toward body

* Stand: Take no more cards; also known as “stand pat”, “stick”, or “stay”.

signal: (handheld) Slide cards under chips. (face up) Wave hand horizontally.

* Double down (only available as first decision of a hand): The player is allowed to increase the initial bet by up to 100% in exchange for committing to stand after receiving exactly one more card. The additional bet is placed in the betting box next to the original bet. Some games do not permit the player to increase the bet by amounts other than 100%. Non-controlling players may double their wager or decline to do so, but they are bound by the controlling player’s decision to take only one card.

signal: Place additional chips beside the original bet, and point with one finger.

* Split (only available as first decision of a hand): If the first two cards have the same value, the player can split them into two hands, by moving a second bet equal to the first into an area outside the betting box of the original bet. The dealer separates the two cards and draws a further card on each, placing one bet with each hand. The player then plays out the two separate hands in turn, with some restrictions. Occasionally, in the case of ten-valued cards, some casinos allow splitting only when the cards have the identical ranks; for instance, a hand of T-T may be split, but not of T-K. However, usually all ten-value cards are treated the same. Doubling and further splitting of post-split hands may be restricted, and blackjacks after a split are counted as non-blackjack 21 when comparing against the dealer’s hand. Hitting split aces is usually not allowed. Non-controlling players may follow the controlling player by putting down an additional bet, or decline to do so, instead associating their existing wager with one of the two post-split hands. In that case they must choose which hand to play behind before the second cards are drawn.

signal: Place additional chips next to the original bet outside the betting box. Point with two fingers spread into a V formation.

* Surrender (only available as first decision of a hand): Some games offer the option to “surrender”, usually in hole card games and directly after the dealer has checked for blackjack (but see below for variations). When the player surrenders, the house takes half the player’s bet and return the other half to the player; this terminates the player’s interest in the hand. The request to surrender is made verbally, there being no standard hand signal.