Encyclopaedia Britannica Online Shop

0-9

Achagua ... acrolith

Achagua: South American Indian people of Venezuela and eastern Colombia. They speak a language of the Maipurean Arawakan group. Traditionally, the Achagua had typical tropical-forest economies, living in large villages and ...
Ache: nomadic South American Indian people living in eastern Paraguay. The Ache speak a Tupian dialect of the Tupi-Guaranian language family. They live in the densely forested, hilly region between the ...
Acheampong, Ignatius Kutu: Ghanaian army officer, who, after leading a military revolt that overthrew the government of Kofi Busia, became Ghana's chief of state in 1972. In July 1978 he was forced to ...
Achebe, Chinua: prominent Igbo (Ibo) novelist acclaimed for his unsentimental depictions of the social and psychological disorientation accompanying the imposition of Western customs and values upon traditional African society. His particular concern ...
Achelous River: one of the longest rivers in Greece, rising in the Pindus Mountains of central Epirus (Ipiros) and dividing Aetolia from Acarnania. It debouches into the Ionian Sea after a course ...
Achenbach, Andreas: landscape painter, a pioneer of the German realist school. He studied at the Dusseldorf academy under Johann Wilhelm Schirmer, but emancipated himself from the contemporary school of landscapists that delighted ...
achene: dry, one-seeded fruit lacking special seams that split to release the seed. The seed coat is attached to the thin, dry ovary wall (husk) by a short stalk, so that ...
Achernar: brightest star in the southern constellation Eridanus and one of the 10 brightest stars in the sky, with an apparent visual magnitude of 0.47. It lies about 60 or 70 ...
Acheron: river in Thesprotia in Epirus, Greece, that was thought in ancient times to go to Hades because it flowed through dark gorges and went underground in several places; an oracle ...
Acheson, Dean: U.S. secretary of state (1949-53) and adviser to four presidents, who became the principal creator of U.S. foreign policy in the Cold War period following World War II; he helped ...
Acheson, Edward Goodrich: American inventor who discovered the abrasive Carborundum and perfected a method for making graphite.
Acheulean industry: first standardized tradition of toolmaking of Homo erectus and early Homo sapiens. Named for the type site, Saint-Acheul, in Somme departement, in northern France, Acheulean tools were made of stone ...
Achill Island: mountainous island off the west coast of Ireland. It is part of County Mayo, joined to the mainland by a bridge across Achill Sound. The island is Ireland's largest, with ...
Achilles: in Greek mythology, son of the mortal Peleus, king of the Myrmidons, and the Nereid, or sea nymph, Thetis. He was the bravest, handsomest, and greatest warrior of the army ...
Achilles Painter: Athenian vase painter known by and named for an amphora attributed to him with a painting of "Achilles and Briseis." The amphora is now in the Vatican Museums. His period ...
Achilles paradox: in logic, an argument attributed to the 5th-century BC Greek philosopher Zeno, and one of his four paradoxes described by Aristotle in the treatise Physics. The paradox concerns a race ...
Achilles Tatius: teacher of rhetoric and author of Leucippe and Cleitophon, one of the Greek prose romances that influenced the development of the novel centuries later.
Achilles tendon: strong tendon at the back of the heel that connects the calf muscles to the heel. The tendon is formed from the gastrocnemius and soleus muscles (the calf muscles) and ...
Achillini, Alessandro: Italian philosopher and physician, an advocate of the teachings of William of Ockham.
Achinese: one of the main ethnic groups on the island of Sumatra, Indonesia. They were estimated to number roughly 2,100,000 in the late 20th century. They speak a language of the ...
Achinese War: (1873-1904), an armed conflict between The Netherlands and the Muslim sultanate of Acheh (now Aceh) in northern Sumatra that resulted in Dutch conquest of the Achinese and, ultimately, in Dutch ...
Achinsk: city, Krasnoyarsk kray (region), south-central Russia. It lies along the Chulym River, which is a tributary of the Ob. It was founded in 1621 and chartered in 1782. Important as ...
Acholi: ethnolinguistic group of northern Uganda and southernmost Sudan. Numbering more than one million at the turn of the 21st century, they speak a Western Nilotic language of the Eastern Sudanic ...
achondrite: any stony meteorite containing no chondrules (rounded granules of cosmic origin). Achondrites, constituting about 4 percent of the known meteorites, are similar in appearance to terrestrial igneous rocks low in ...
achondroplasia: genetic disorder characterized by a lack of cartilage cells. As a consequence, bones that depend on cartilage models for development cannot grow. Achondroplasia is the most common cause of dwarfism. ...
Achterberg, Gerrit: Dutch poet whose use of surreal language and imagery influenced a generation of post-World War II poets known as the Experimentalists. His verse, traditional in form, is characterized as romantic ...
acid: any substance that in water solution tastes sour, changes the colour of certain indicators (e.g., reddens blue litmus paper), reacts with some metals (e.g., iron) to liberate hydrogen, reacts with ...
acid and basic rocks: division of igneous rocks on the basis of their silica content. Chemical analyses of the most abundant components in rocks usually are presented as oxides of the elements; igneous rocks ...
acid dye: any bright-coloured synthetic organic compound whose molecule contains two groups of atoms-one acidic, such as a carboxylic group, and one colour-producing, such as an azo or nitro group. Acid dyes ...
acid halide: neutral compound that reacts with water to produce an acid and a hydrogen halide. Acid halides are ordinarily derived from acids or their salts by replacement of hydroxyl groups by ...
acid rain: form of precipitation containing a heavy concentration of sulfuric and nitric acids. The term is also commonly applied to snow, sleet, and hail that manifest similar acidification. Such precipitation has ...
acid-base catalysis: acceleration of a chemical reaction by the addition of an acid or a base, the acid or base itself not being consumed in the reaction. The catalytic reaction may be ...
acid-base reaction: a type of chemical process typified by the exchange of one or more hydrogen ions, H⁺, between species that may be neutral (molecules, such as water, H₂O; or acetic acid, ...
acidosis: abnormally high level of acidity, or low level of alkalinity, in the body fluids, including the blood. Acidosis may be respiratory or metabolic in origin. The former may result from ...
Acireale: town and episcopal see, Catania provincia, eastern Sicily, Italy, on terraces above the Ionian Sea at the foot of Mount Etna, 7 miles (11 km) northeast of Catania. Known as ...
Acis: in the Greek mythology of Ovid, the son of Faunus (Pan) and the nymph Symaethis. He was a beautiful shepherd of Sicily, the lover of the Nereid Galatea. His rival, ...
Acker, Kathy: American novelist whose writing style and subject matter reflect the so-called punk sensibility that emerged in the 1970s.
Ackerley, J.R.: British novelist, dramatist, poet, and magazine editor known for his eccentricity.
Ackerman, Diane: American writer whose works often reflect her interest in natural science.
Ackermann, Konrad Ernst: actor-manager who was a leading figure in the development of German theatre.
Ackermann, Louise-Victorine: French poet who is best-known for works characterized by a deep sense of pessimism.
Ackroyd, Peter: British novelist, critic, biographer, and scholar whose technically innovative novels present an unconventional view of history.
Acmeist: member of a small group of early-20th-century Russian poets reacting against the vagueness and affectations of Symbolism. It was formed by the poets Sergey Gorodetsky and Nikolay S. Gumilyov. They ...
acne: any inflammatory disease of the sebaceous, or oil, glands of the skin. There are some 50 different types of acne. In common usage, the term acne is frequently used alone ...
Acoemeti: monks at a series of 5th- to 6th-century Byzantine monasteries who were noted for their choral recitation of the divine office in constant and never interrupted relays. Their first monastery, ...
acolyte: (from Greek akolouthos, "server," "companion," or "follower"), in the Roman Catholic church, a person is installed in a ministry in order to assist the deacon and priest in liturgical celebrations, ...
Acoma: Indian pueblo, Valencia county, west-central New Mexico, U.S. The pueblo lies 55 miles (89 km) west-southwest of Albuquerque and is known as the "Sky City." Its inhabitants live in terraced ...
Aconcagua River: river in central Chile. It rises in the northwestern foothills of Mount Aconcagua of the Andes Mountains and flows westward from the Argentine border area through Valparaiso
Aconcagua, Mount: mountain in Argentina. It is commonly regarded as the highest summit in the Western Hemisphere, rising 22,834 feet (6,959 metres) above sea level. Aconcagua lies in the Southern Andes, its ...
aconite: any member of two genera of perennial herbs of the buttercup family (Ranunculaceae): Aconitum, consisting of summer-flowering poisonous plants (see monkshood), and Eranthis, consisting of spring-flowering ornamentals (see winter aconite).
Acontius: in Greek legend, a beautiful youth of the island of Ceos. During the festival of Artemis at Delos, Acontius saw and loved Cydippe, a girl of a rich and noble ...
Acontius, Jacobus: advocate of religious toleration during the Reformation whose revolt took a more extreme form than that of Lutheranism.
acorn and nut weevil: any of about 45 species of weevils that make up the subfamily Curculioninae of the family Curculionidae (order Coleoptera). The insects have extremely long and slender snouts, which in females ...
acorn worm: any of the soft-bodied invertebrates of the class Enteropneusta, phylum Hemichordata. The front end of these animals is shaped like an acorn, hence their common name. The "acorn" consists of ...
acosmism: in philosophy, the view that God is the sole and ultimate reality and that finite objects and events have no independent existence. Acosmism has been equated with pantheism, the belief ...
Acosta, Joaquin: Colombian scientist, historian, and statesman who sought to preserve knowledge of his country's early history.
Acosta, Jose de: Jesuit theologian and missionary to the New World, chiefly known for his Historia natural y moral de las Indias, the earliest survey of the New World and its relation to ...
Acosta, Uriel: freethinking rationalist who became an example among Jews of one martyred by the intolerance of his own religious community. He is sometimes cited as a forerunner of the renowned philosopher ...
acouchy: either of two species of South American rodents that resemble the small tropical-forest-dwelling hoofed animals of Africa and Asia (see royal antelope; chevrotain). Weighing 1 to 1.5 kg (2.2 to ...
acoustic impedance: absorption of sound in a medium, equal to the ratio of the sound pressure at a boundary surface to the sound flux (flow velocity of the particles or volume velocity, ...
acoustic interferometer: device for measuring the velocity and absorption of sound waves in a gas or liquid. A vibrating crystal creates the waves that are radiated continuously into the fluid medium, striking ...
acoustic neuroma: benign tumour on the vestibulocochlear nerve (also called acoustic nerve) near its point of entry into the inner ear. The tumour, though benign, may spread into the brain cavity if ...
acoustic trauma: physiological changes in the body caused by sound waves. Sound waves cause variations in pressure, the intensity of which depends upon the range of oscillation, the force exerting the sound, ...
acoustics: the science concerned with the production, control, transmission, reception, and effects of sound. The term is derived from the Greek akoustos, meaning "hearing."
acquired character: in biology, modification in structure or function acquired by an organism during its life, caused by environmental factors. With respect to higher organisms, there is no evidence that such changes ...
acquittal: in criminal law, acknowledgment by the court of the innocence of the defendant or defendants. Such a judgment may be made by a jury in a trial or by a ...
Acrasieae: class name for cellular slime molds (division Myxomycophyta). The class contains a single order, Acrasiales, and about a dozen species. The vegetative phase of these slime molds consists of amoeba-like ...
acre: unit of land measurement in the British Imperial and United States Customary systems, equal to 43,560 square feet, or 160 square rods. One acre is equivalent to 0.4047 hectares (4,047 ...
Acre: westernmost estado ("state") of Brazil. Acre covers the southwesternmost part of Brazil's Hileia (Hylea), the forest zone of the Amazon River basin. Bounded north by Amazonas state, ...
Acre River: river, chiefly in western Brazil, rising on the Peruvian border, along which it continues eastward to form part of the Brazil-Bolivia border. Turning north at Brasileia, the remainder of its ...
acriflavine: dye obtained from coal tar, introduced as an antiseptic in 1912 by the German medical-research worker Paul Ehrlich and used extensively in World War I to kill the parasites that ...
Acrisol: one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Acrisols form on old landscapes that have an undulating topography and a humid ...
acrobatics: (Greek: "to walk on tip-toe," or "to climb up"), the specialized and ancient art of jumping, tumbling, and balancing, often later with the use of such apparatus as poles, one-wheel ...
acrocephalosyndactyly: congenital malformation of the skeleton, affecting the skull, hands, and feet, first described by the French pediatrician Eugene Apert. The head is shortened front-to-back and appears pointed (acrocephaly) because of ...
acrocyanosis: uneven reddish-blue discoloration of the hands caused by spasms in arterioles (small arteries) of the skin. Less commonly the feet are affected. The fingers, or toes, are usually cold and ...
acrolith: statue, especially ancient Greek, in which the trunk of the figure was of wood and the head, hands, and feet of marble. The wood was either gilded or covered by ...