A domino is a small rectangular wood or plastic block, the face of which is marked with an arrangement of dots resembling those on dice. Each end of a domino has a number showing on it, with the lower number being listed first. Each domino may also have a blank side, in which case the value is zero. A domino is a base for many games and is often used to create chains of dominoes, which are built up by placing one domino edge-to-edge on top of another.

Dominoes are a common element of family and party games. They can be used in conjunction with cards, dice and other game pieces to play a variety of games. The most popular type of domino game is a layout game, in which players alternately place tiles on the table. The goal of these games is to build a chain of dominoes, starting from the center of the table, and extending outwards in all directions.

In a domino game, the rules vary according to the particular layout game being played. Most rules involve a set number of tiles that must be matched in order to form a chain. Players must then “knock out” the opponent’s tiles by playing a domino with a matching number on either its end or its blank side. Once a player has “knocked out” an opposing player’s domino, that player must leave the rest of his or her tiles face-down on the table, and may only add more tiles to the end of the chain which have matching numbers on both ends.

The word “domino” has a long history and is sometimes used in idioms, such as the phrase “dropping like a domino.” The phrase refers to any action that has an effect similar to a domino falling—a sequence of events that builds up momentum until it reaches a critical point at which it bursts into motion.

The term has been in use since at least the mid-19th century, and may be derived from the Latin dominum, meaning a flat or elongated piece of material. The first documented use of the word as a name for a game is in an 1837 book by John A. McCreery, and it is believed that this may have inspired the name for a popular card game. The word was added to the American Dialect Dictionary in 1906, and to the Oxford English Dictionary in 1907. Today, the term is used primarily in reference to games involving the placement of dominoes on the table. Many dominoes are set up in carefully constructed patterns, and builders compete to demonstrate their ability to create the most complex domino effects before a crowd of spectators at domino shows.