Rummy is a group of card games notable for game play based on the matching of similar playing cards. David Palette (The Penguin Book of Card Games, 1978) describes the Mexican game of Coquina as being ancestral to all rummy games, which itself is derived from a Chinese game called Khanhoo and, going even further back, Mahjong.

A book consists of at least three cards of the same rank or consecutive cards of the same suit. This is an almost universal pattern, although there exist minor variations, such as allowing only melds of the first type or requiring in melds of the second type that the cards are all of a different suit. In some games it is required that the melds of the second type contain at least four cards. Some games also feature wild cards, which can be used to represent any card in a meld. The number of wild cards in a meld may be restricted.

In the card game of Rummy, two people playing get ten cards each. When there are more than two people, fewer cards are dealt to each player. The person left of the dealer is the first person to play. The dealer switches from person to person going to the left. The dealer flips one card to and places it next to the pile to begin the game.

The first person to go takes a card from the deck or the card placed beside it. When the player has done that, they may either put three cards of the same number or a straight. After this is done, or if they do not make a play at all, a card from their hand is discarded onto the pile beside the deck.

In two player rummy, each player gets ten cards. Starting with the player to the dealer's left, cards are dealt clockwise, face down, one at a time. The dealer then puts the rest of the deck, face down, between the players. This forms the stock pile. A single card is then drawn and placed face up next to the stack. This is called the discard pile.

If a player has three cards of the same suit in a sequence (called a sequence or a run), they may meld by laying these cards, face up, in front of them. If they have at least three cards of the same value, they may meld a group (also called a set or a book). Melding is optional. A player may choose, for reasons of strategy, not to meld on a particular turn. The most important reason is to be able to declare "Rummy" later in the game.