Seasonal variations in groundwater levels.
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Game similar to lawn tennis that is played on a tabletop with wooden paddles and a small, hollow, plastic ball. The object is to hit the ball so that it goes over the net and bounces on the opponent's half of the table in such a way as to defeat the opponent's attempt to reach and return it. Both singles and doubles games are played. A match consists of the best of any odd number of games, each game being won by the player or team who first reaches 11 points or who, after 10 points each, gains a two-point lead. Invented in England in the early 20th century, it soon spread throughout the world. Since the mid-1950s, East Asian countries have dominated the sport. It has been an Olympic sport for both men and women since 1988.
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Article of furniture used in the Western world since at least the 7th century BC, consisting of a flat slab of stone, metal, wood, or glass supported by trestles, legs, or a pillar. Though tables were used in ancient Egypt, Assyria, and Greece, only during the Middle Ages, with the growing formality of life under feudalism, did tables increasingly take on social significance. Tables with attached legs appeared in the 15th century. The draw top was invented in the 16th century, making it possible to double the table length. Increasing contact with the East in the 18th century led to increasing specialization in the design of occasional tables.
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Organized array of all the chemical elements in approximately increasing order of their atomic weight. The elements show a periodic recurrence of certain properties, first discovered in 1869 by Dmitry I. Mendeleyev. Those in the same column (group) of the table as usually arranged have similar properties. In the 20th century, when the structure of atoms was understood, the table was seen to precisely reflect increasing order of atomic number. Members of the same group in the table have the same number of electrons in the outermost shells of their atoms and form bonds of the same type, usually with the same valence; the noble gases, with full outer shells, generally do not form bonds. The periodic table has thus greatly deepened understanding of bonding and chemical behaviour. It also allowed the prediction of new elements, many of which were later discovered or synthesized. For an illustration of the periodic table, see chemical element.
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Inlet, Atlantic Ocean, forming the harbour of Cape Town, South Africa. It is 12 mi (19 km) long and 8 mi (12 km) wide. Although less sheltered than other bays along the coast, it became a port of call for ships traveling to India and the East because of the availability of fresh water. The shore was permanently settled by the Dutch in 1652.
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