Is a lottery-like gambling game often played at modern casinos, and also offered as a game by some lotteries.
Players wager by choosing numbers ranging from 1 through (usually) 80.
After all players make their wagers, 20 numbers (some variants draw fewer numbers) are drawn at random, either with a ball machine similar to ones used for lotteries and bingo, or with a random number generator.
Each casino sets its own series of payouts, called "paytables".
The player is paid based on how many numbers were chosen (either player selection, or the terminal picking the numbers), the number of matches out of those chosen, and the wager.
There are a wide variety of keno paytables depending on the casino, usually with a larger "house edge" than other games offered by that casino.
The house edge ranges from less than 4 percent The word keno has French or Latin roots (Fr. quini "five each"), but by all accounts the game originated in China.
Legend has it that the invention of the game saved an ancient city in time of war, and its widespread popularity helped raise funds to build the Great Wall of China.
In modern China, the idea of using lotteries to fund a public institution was not accepted before the late 19th century.
Chinese lotteries are not documented before 1847 when the Portuguese government of Macau decided to grant a license to lottery operators.
According to some, results of keno games in great cities were sent to outlying villages and hamlets by carrier pigeons, resulting in its Chinese name 白鸽票 báigē piào, literally "white dove ticket", pronounced baak-gap-piu in Cantonese (on which the Western spelling 'pak-ah-pu' / 'pakapoo' was based).
The Chinese played the game using sheets printed with Chinese characters, often the first 80 characters of the Thousand Character Classic, from which the winning characters were selected.