A slot is a narrow notch, groove or opening. A slot can be used to hold a key or a coin.

A player inserts cash or, in “ticket-in, ticket-out” machines, a paper ticket with a barcode into a slot on a machine to activate it. The machine then rearranges the symbols and pays out credits based on the paytable. Most slot games have a theme, and the symbols and bonus features are aligned with that theme. In addition, most slots have a particular RTP (return to player) rate and variance (how much the game fluctuates between wins and losses), which are indicated somewhere on the casino’s website or in the game rules.

In programming, a slot is an object that allows a private function to be invoked from any instance of the class it is attached to, without exposing its public interface. This is accomplished by using a signal-slot connection, and reduces the amount of memory that must be allocated for each call to a private function. However, this approach is somewhat slower than calling a method directly, because the signal-slot connection requires a non-virtual function call to locate and safely iterate over all connected receivers. This overhead is negligible in most applications, though.