pool

Pool commonly refers to a man-made basin filled with water used for swimming and recreation. The term also denotes a cue sport played on a rectangular table with six pockets, as well as a collective pool of money or resources contributed for a common purpose. Pools may be indoor or outdoor, public or private, and vary in size and construction.

Swimming pools typically consist of a concrete or reinforced shell lined with plaster, tiles, vinyl, or fiberglass. Water is circulated by a pump through a filtration system and sanitised with chlorine, bromine, or saltwater systems. Heating, covers, and safety features such as fences or alarms are common. Maintenance includes balancing pH and sanitizer levels, cleaning debris, and inspecting equipment.

Pool games are played on tables with six pockets and a cue ball, using numbered object balls. In 8-ball, players are assigned stripes or solids and aim to pocket all of their group, then the 8-ball. In 9-ball, players must hit the lowest-numbered ball first and aim for the 9-ball. International competition is governed by the World Pool-Billiard Association, with national bodies such as the Billiard Congress of America. Equipment includes cues, chalk, and tables typically 4.5 by 9 feet or larger.

Beyond physical pools, “pool” can mean a shared fund or resource pool, into which participants contribute for a common purpose. This concept appears in betting pools, insurance pools, and collaborative investment pools, and in economics and operations research as a means to spread risk or costs.