A domino is a small rectangular block, thumbsized or slightly larger, that is blank or marked by dots or pips resembling those on dice. Twenty-eight such tiles form a full set of dominoes for use in various games. Dominoes are often stacked in long lines, each one touching and affecting the next in a sequence known as a domino effect. The term is also used to refer to a chain reaction of events, such as an earthquake triggering a series of tsunamis. In the social sciences, the term is sometimes used to describe a pattern of behaviors in which changes to one cause shifts in related behavior. For example, a person may decide to exercise more and eat less fat as a result of watching a friend lose weight.

The word domino derives from the Latin dominica, meaning “flag” or “sign of the flag.” The name has since come to refer to a general orderly and well-arranged system.

Dominoes are a popular children’s toy, but many adults play them as well. A basic Western set contains 28 dominoes, and larger sets with more tiles are available for use in more advanced games. Some people also collect and create elaborate domino constructions that are displayed in their homes or at public gatherings.

A common rule in most domino games is that a player must lay a tile adjacent to an already-played tile to continue play, except when the resulting combination of three or more tiles makes a cross or some other specified total. This rule ensures that all players are able to play at least one turn, and it limits the amount of time that any one player can spend on his or her turn.

Some games have special rules for placing or removing certain types of dominoes from the table. The simplest and most common of these rules is called drawing, where each player draws two or more dominoes from the stock until a player has a number that can be played. The player then places the drawn dominoes, face down, on the table so that their pips line up with those of the previously-played dominoes.

The most basic Western domino games are blocking and scoring games for two or more players. In a blocking game, each player plays against all of the other players’ pieces simultaneously. The winning player is the first to complete a block of pieces, which is usually done by matching the ends of adjacent dominoes or filling in all empty spaces.

Dominoes may be arranged in the form of squares, lines, or angular patterns. They can also be stacked on end in a long row, as in the picture below. When a domino in the middle is tipped over, it causes all of the other dominoes to fall over in an elegant cascade of rhythmic motion. A similar type of pattern can be created by pushing a piece of paper on top of a stack of books.