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canal

(Encyclopedia)canal, an artificial waterway constructed for navigation or for the movement of water. The digging of canals for irrigation probably dates back to the beginnings of agriculture, and traces of canals h...

Pacific Ocean

(Encyclopedia)CE5 Pacific Ocean, largest and deepest ocean, c.70,000,000 sq mi (181,300,000 sq km), occupying about one third of the earth's surface; named by the explorer Ferdinand Magellan; the southern part i...

Confederation, Articles of

(Encyclopedia)Confederation, Articles of, in U.S. history, ratified in 1781 and superseded by the Constitution of the United States in 1789. The imperative need for unity among the new states created by the America...

child abuse

(Encyclopedia)child abuse, physical, sexual, or emotional maltreatment or neglect of children by parents, guardians, or others responsible for a child's welfare. Physical abuse is characterized by physical injury, ...

map projection

(Encyclopedia)map projection, transfer of the features of the surface of the earth or another spherical body onto a flat sheet of paper. Only a globe can represent accurately the shape, orientation, and relative ar...

wave, in physics

(Encyclopedia)wave, in physics, the transfer of energy by the regular vibration, or oscillatory motion, either of some material medium or by the variation in magnitude of the field vectors of an electromagnetic fie...

X ray

(Encyclopedia)CE5 Typical X-ray composite spectrum (intensity as a function of frequency) X ray, invisible, highly penetrating electromagnetic radiation of much shorter wavelength (higher frequency) than visibl...

ecology

(Encyclopedia)ecology, study of the relationships of organisms to their physical environment and to one another. The study of an individual organism or a single species is termed autecology; the study of groups of ...

ion, in chemistry

(Encyclopedia)ion, atom or group of atoms having a net electric charge. Ionization has many applications. Vapor lamps and fluorescent lamps take advantage of the light given off when positive ions recombine with ...

Johnson, Lyndon Baines

(Encyclopedia)Johnson, Lyndon Baines, 1908–73, 36th President of the United States (1963–69), b. near Stonewall, Tex. Johnson lost the 1960 Democratic presidential nomination to John F. Kennedy, but accepte...