A slot is a position or time within which something can be put into place. A slot is also the name of a device that can be used to hold a paper document or card, such as a photo album cover or a postcard.

The term slot is also used to describe an authorization of a planned aircraft operation at an airport. This is a tool that is used in the United States and around the world to manage air traffic at extremely busy airports, and to prevent repeated delays caused by too many flights trying to take off or land at the same time.

Slots are a very popular form of gambling machine. They are designed to attract players by offering high-frequency, attention-grabbing rewards. However, a significant percentage of people who play slots do not enjoy gambling and may develop severe problems (Abbot & Volberg, 1996; Getty, Watson, & Frisch, 2000). These include financial difficulties, personal and professional problems, and substance abuse.

The first slot machines were electromechanical, with reels that were operated by pulling a lever or button. Modern video slot machines have digital technology that simulates reels on a monitor. They can have a single pay line or multiple lines that run across the screen and can feature wild symbols that substitute for other symbols. Some machines also have bonus rounds that offer additional chances to win. These bonus rounds may be played on a separate mechanical device or on an animated screen.