What is a Slot?

— A narrow notch, groove, or opening, as a keyway in machinery or a slit for a coin in a vending machine. – Webster’s New World College Dictionary, 4th Edition Copyright 2010 by Houghton Mifflin Harcourt. All rights reserved.

In a casino, a slot is a place for a slot machine to take wagers and activate games for each spin. Until recently — and still in some locations today — players dropped coins into slots to make a bet. That changed with the introduction of bill validators and credit meters, which made it easier to think of wagers as credits rather than coins.

Modern machines use the same principles as their mechanical ancestors: a lever or button pull activates motors that spin reels and stop them at random. The outcome of a spin is determined by whether or not matching symbols line up on the pay line, a vertical line in the center of the machine. In older machines, this information was read by a reel-scanning mechanism; in electrical machines, it is read by a computer program.

A slot game’s odds are based on its probability, which is computed by a computer chip that makes thousands of mathematical calculations each second. This process is known as a Random Number Generator (RNG). A machine’s programmed payout percentage is designed to balance the house edge against its popularity. If the machine pays out more often than it takes in, it’s said to be hot. If it pays out less often, it’s called cold.