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Lorentz contraction

(Encyclopedia)Lorentz contraction lôrˈĕnts [key], in physics, contraction or foreshortening of a moving body in the direction of its motion, proposed by H. A. Lorentz on theoretical grounds and based on an earli...

uncertainty principle

(Encyclopedia)uncertainty principle, physical principle, enunciated by Werner Heisenberg in 1927, that places an absolute, theoretical limit on the combined accuracy of certain pairs of simultaneous, related measur...

barbiturate

(Encyclopedia)barbiturate bärbĭchˈərātˌ [key], any one of a group of drugs that act as depressants on the central nervous system. High doses depress both nerve and muscle activity and inhibit oxygen consumpti...

lung cancer

(Encyclopedia)lung cancer, cancer that originates in the tissues of the lungs. Lung cancer is the leading cause of cancer death in the United States in both men and women. Like other cancers, lung cancer occurs aft...

damselfish

(Encyclopedia)damselfish, common name for members of the large family Pomacentridae, marine fishes of tropical waters. Common in the West Indies and along the Florida coasts are the sergeant-major, named for its ve...

Latin American Integration Association

(Encyclopedia)Latin American Integration Association (LAIA), organization formed in 1980 by Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Mexico, Paraguay, Peru, Uruguay, and Venezuela, taking over the duti...

butterfly fish

(Encyclopedia)butterfly fish, common name for certain members of the Chaetodontidae, a family of reef-dwelling tropical fishes with compressed bodies and small mouths and teeth. Butterfly fish are carnivorous, feed...

tern

(Encyclopedia)tern, common name for a sea bird of the Old and New Worlds, smaller than the related gull. Because of their graceful flight and their long pointed wings and forked tails, some terns are called sea swa...

clan

(Encyclopedia)clan, social group based on actual or alleged unilineal descent from a common ancestor. Such groups have been known in all parts of the world and include some that claim the parentage or special prote...

pear

(Encyclopedia)pear, name for a fruit tree of the genus Pyrus of the family Rosaceae (rose family) and for its fruit, a pome. The common pear (P. communis) is one of the earliest cultivated of fruit trees, both in i...