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division, in mathematics

(Encyclopedia)division, fundamental operation in arithmetic; the inverse of multiplication. Division may be indicated by the symbol ÷, as in 15 ÷ 3, or simply by a fraction, 15/3. The number that is being divided...

exponent

(Encyclopedia)exponent, in mathematics, a number, letter, or algebraic expression written above and to the right of another number, letter, or expression called the base. In the expressions x2 and xn, the number 2 ...

hydroponics

(Encyclopedia)hydroponics, growing of plants without soil in water to which nutrients have been added. Hydroponics has been used for over a century as a research technique, but not until 1929 were experiments condu...

Godolphin, Sidney Godolphin, 1st earl of

(Encyclopedia)Godolphin, Sidney Godolphin, 1st earl of gədŏlˈfĭn [key], 1645–1712, English statesman. He early established a lasting friendship with John Churchill (later duke of Marlborough), and their polit...

attention deficit hyperactivity disorder

(Encyclopedia)attention deficit hyperactivity disorder (ADHD), formerly called hyperkinesis or minimal brain dysfunction, a chronic, neurologically based syndrome characterized by any or all of three types of behav...

Northern Cape

(Encyclopedia)Northern Cape, province (2011 pop. 1,145,861), 144,015 sq mi (372,889 sq km), NW South Africa. In 1994, under South Africa's post-apartheid constitution, Northern Cape was created from the northern po...

Ouattara, Alassane

(Encyclopedia)Ouattara, Alassane äläsänˈ wäˈtärä [key], 1942–, Ivorian economist and politician, grad. Univ. of Pennsylvania (M.A. 1967, Ph.D. 1972). A Muslim from N Côte d'Ivoire, he worked at the Inter...

Powell, John Wesley

(Encyclopedia)Powell, John Wesley, 1834–1902, American geologist and ethnologist, b. Mt. Morris (now part of New York City). The family moved to Illinois, where Powell joined the Natural History Society, making c...

tar and pitch

(Encyclopedia)tar and pitch, viscous, dark-brown to black substances obtained by the destructive distillation of coal, wood, petroleum, peat, and certain other organic materials. The heating or partial burning of w...

thyrotropin

(Encyclopedia)thyrotropin thīˌrätrōˈpĭn [key] or thyroid-stimulating hormone (TSH), hormone released by the anterior pituitary gland that stimulates the thyroid gland to release thyroxine. The release of thyr...