A domino is a small rectangular wood or plastic block with a blank or identically patterned face, or with one side bearing an arrangement of dots resembling those on dice. It is used in games that involve the placement of these blocks so that adjacent ones topple, often creating long chains. The word is also used as a noun to refer to a set of these tiles and, more broadly, to any game played with them. Dominos may be used to form straight or curved lines, grids that can be arranged to make pictures, or stacked walls.

As soon as the first domino is toppled, a chain reaction begins that causes all the rest of them to fall over in turn. This happens because a domino has a certain amount of potential energy. This energy is stored in the shape and materials of the domino and the surface on which it sits, and a little friction between the two causes them to rub together, converting some of this potential energy into heat and sound.

The process of plotting a novel can be compared to the falling of dominoes: a writer has to carefully consider what will happen to his or her characters after each step, and build in all the reactions that could result. A good way to do this is to create an outline, a structure of notes that lays out the main events in a story, and the chain reactions that would occur as each event is followed by the next. The outline can be as detailed or as vague as a writer wishes, but it must cover every possible action and consequence to ensure that there is nothing left to chance.

There are countless variations on the game of domino, with some having nearly identical rules and others differing in details from place to place. For example, the rule that a player who plays a double can immediately play another tile on that same double (called “the lead” or the “first play”) is different from the rule in many places.

The most popular domino games are bidding and blocking games. In these, players compete for the opportunity to play a tile on a particular end of a domino chain that is either already in place or that can be built up to that point in order to score points. The count of ends of a line of play in these games is determined by counting the number of pips on each end that has been played.

Some players like to use their dominoes to create artistic designs, such as a zigzagging path or a picture frame. There are even domino artists who create intricate creations to be placed on television and movie sets. The most famous of these is Lily Hevesh, who has amassed more than 2 million subscribers to her YouTube channel, where she shares videos of her domino art.