A slot is a container that can be filled with dynamic content. Slots are either passive and wait for content to be called (a waiting slot), or they can actively call out for content with a slot action or a targeter. Slots work in tandem with scenarios to deliver the content to a page, and they also interact with renderers to specify how the content should be presented.

In casino games, a slot is a vertical column of symbols that spin after a lever or button is pressed. When a combination of symbols land in a winning position, the player receives credits based on the pay table. The symbols and features vary from machine to machine, but most are aligned with a theme.

The earliest slots were mechanical, with reels that rotated when the lever was pulled or a button was pressed. Modern slot machines have electronic components that control the spinning of the reels and the weighting of individual symbols. The weighting of the symbols is based on the probability of hitting particular symbols, or a specific combination of symbols, and is programmed into each machine.

In aviation, a slot is an allocated time for an aircraft to take off or land at an airport. This is used when the airport is constrained, either in terms of runway throughput or available parking space. It’s been twenty years since Europe introduced central flow management, and there have been major savings in delays and fuel burn as a result.