Billiards

Billiards descends from outdoor lawn games played in 15th-century Europe, in which players used a stick called a mace to knock balls across grass. As the game moved indoors, players set up a wooden table bordered by rails and covered in green cloth to imitate the lawn it replaced. By around 1850 the billiard table had essentially taken the form still recognizable today, with a 2:1 ratio of length to width that remains standard on every regulation table.

In the United States, the game's growth is closely tied to Michael Phelan, an Irish immigrant who published Billiards Without a Master in 1850 -- the first American book on the subject and a bestseller that helped popularize the game. More formal, standardized rules followed later in the 19th century as the sport organized itself for serious competition.

The terms are often used interchangeably, but they describe related, distinct games with different tables and equipment. "Billiards" traditionally refers to carom billiards, played with just three balls on a pocketless table, where the object is to carom the cue ball off both other balls rather than sink anything. "Pool" -- the pocketed game most people picture in casual American usage -- got its name from poolrooms, betting parlors that installed pocket billiards tables for patrons to play between wagers.

Snooker, played on a larger table with smaller pockets and 21 numbered balls plus a cue ball, developed separately in the 19th century. The regulation 9-foot table and 2.25-inch ball referenced in tournament pool specifications apply specifically to pocket billiards, not to carom billiards or snooker, which use different table and ball dimensions entirely.