averts \'a-venz\ Any of the low-growing, perennial flowering plants (approximately 50 species) of the genus Geum, in the rose family. Most occur in the northern or southern temperate zones or in the Arctic. Several species are cultivated for their solitary or clustered white, red, orange, or yellow flowers. The plants grow no more than 2 ft (60 cm) tall. Most of the compound, deeply lobed or cut leaves arise from the base of the stem.
average See mean, median, and mode
Avernus \3- , v3r-n3s\ / Lake ancient Lacus Avernus. Lake, southern Italy. It lies west of Naples in the crater of an extinct volcano. Because of its sulfurous vapors, it was considered an entrance to the underworld by the ancient Romans, including Virgil. According to legend, the grove of Hecate and the grotto of the Cumaean Sibyl lay nearby. In the 1st century bc it was transformed into a naval base, Portus Iulius, by Agrippa and linked to the sea. Its impressive Roman ruins include baths, temples, and villas.
Averroes \9-'ver-9-,wez \ Arabic Ibn Rushd \,ib-9n-'rusht\ in full Abu al-Walld Muhammad ibn Ahmad ibn Muhammad ibn Rushd (b. 1126, Cordoba—d. 1198, Marrakech, Almohad empire) Span¬ ish Arabic philosopher. Trained in law, medicine, and philosophy, he rose to be chief judge of Cordoba, an office also once held by his grandfather. His series of commentaries on most of the works of Aristotle, written between 1169 and 1195, exerted considerable influence on both Jewish and Christian scholars in later centuries. While mostly faithful to Aristo¬ tle’s thought, he endowed the Aristotelian “prime mover” with the char¬ acteristics of the Plotinian (see Plotinus) and Islamic transcendent God, the universal First Cause. In his Commentary on Plato's Republic he attempted to apply Platonic doctrines to the contemporary Almoravid and Almohad states. See also Arabic philosophy.
Avery, Oswald (Theodore) (b. Oct. 21, 1877, Halifax, N.S., Can.—d. Feb. 20, 1955, Nashville, Tenn., U.S.) Canadian-born U.S. bac¬ teriologist. He studied at Colgate University before taking a post at New York’s Rockefeller Institute Hospital. There he discovered transformation, a process by which a change could be introduced into bacteria and passed on to later generations of transformed cells. He and his coworkers reported in 1944 that the substance that caused the transformation was DNA, the cell’s genetic material. The discovery thus opened the door to decipher¬ ing the GENETIC CODE.
Avesta \o-'ves-t3\ or Zend-Avesta Sacred book of Zoroastrianism. It contains hymns, prayers, and appeals to righteousness ascribed to Zoro¬ aster. The present text was assembled in the 3rd-7th century ad from the remains of a larger body of scripture that was destroyed when Alexander the Great conquered Persia. It has five parts: the Gathas, hymns in what are thought to be Zoroaster’s own words; Visp-rat, containing homages
Avalokitesvara, bronze figure from Kurkihar, Bihar, 9th century; in Patna Museum, Patna, Bihar
BY COURTESY OF PATNA MUSEUM, PATNA (BIHAR); PHOTOGRAPH, ROYAL ACADEMY OF ARTS, LONDON
© 2006 Encyclopaedia Britannica, Inc.
Avestan ► Avon I 139
to spiritual leaders; Vendidad, the main source for Zoroastrian law; the Yashts, 21 hymns to angels and ancient heroes; and the Khurda avesta, composed of minor texts.
Avestan \3-'ves-t3n\ language Eastern Iranian language of the Avesta, the sacred book of Zoroastrianism. The oldest portion of the Avesta, the Gathas, are now commonly thought to date from around the end of the 2nd millennium bc and are thus contemporary with Vedic San¬ skrit. Not until the mid-SASANiAN period (5 th—6th century ad) was the Avesta committed to writing, in an alphabetic script invented for the pur¬ pose on the basis of existing Middle Persian scripts. The oldest manu¬ scripts date only from the 13th century.
aviary Structure for keeping captive birds, usually spacious enough for the aviculturist to enter. Aviaries range from small enclosures to large flight cages 100 ft (30 m) or more long and up to 50 ft (15 m) high. Enclosures for birds that fly only little or weakly (e.g., rails, pheasants) may be only about 3 ft (1 m) high. In cold climates the aviary is usually enclosed and heated. Most aviculturists prefer to place birds in natural, planted surroundings. Many aviaries are maintained for pleasure by pri¬ vate aviculturists; others, especially large ones, are found in zoos or research institutions.
aviation Development and operation of aircraft. In 1783 the balloon became the first aircraft to carry humans. Production of a successful glider in 1891 and refinement of the internal-combustion engine led to the first successful engine-powered airplane flight by Wilbur and Orville Wright in 1903. World War I accelerated the expansion of aviation, and in the 1920s the first small airlines began carrying mail and passengers. World War II was another period of innovation in aircraft size, speed, and range. In the late 1940s the jet engine made possible the subsequent development of commercial airlines throughout the world. See also airship; helicopter; sea¬ plane.
Avicenna V.a-vo-'se-noV Arabic Ibn Sina \'ib-3n-'se-na\ in full Abu ’All al-Husayn ibn *Abd Allah ibn STna (b. 980, Bukhara, Iran—d. 1037, Hamadan) Islamic philosopher and scientist. He became physician to several sultans and also twice served as vizier. His Canon of Medicine was long a standard work in the field. He is known for his great encyclopaedia of philosophy, The Book of Healing. His other writings include The Book of Salvation and The Book of Directives and Remarks. His interpretations of Aristotle influenced European Scholasticism. His sys¬ tem rests on a conception of God as the necessary existent: only in God do essence (what God is) and existence (that God is) coincide.
Avignon \,a-ve-'ny6 n \ ancient Avennio City (pop., 2004 prelim.: 89,400), southeastern France. Founded by the Gallic tribe of Cavares, it later fell under Roman rule and was a much-fought-over prize in its early days. Its status grew tremendously as the capital of the papacy (1309-77) and seat of the Avignonese popes during the Western Schism. France annexed the city in 1791. Landmarks include a Romanesque cathedral, the papal palace, and Saint-Benezet bridge, made famous by the song “Sur le pont d’Avignon.” The city’s historic centre was designated a World Heritage site in 1995.
Avignon papacy Roman Catholic papacy during the period 1309-77, when the popes resided at Avignon, France. Elected pope through the machinations of Philip IV of France, Clement V moved the papal capital to Avignon four years later primarily for political reasons. All seven popes of this period were French, as were most of the cardinals, which aroused English and German animosity. During the Avignon papacy the cardinals began to play a stronger role in church government, church and clergy were reformed, missionary efforts were expanded, and popes tried to settle royal rivalries and establish peace. The heavy French influence damaged the prestige of the papacy, however, and in 1377 Gregory XI returned to Rome. The cardinals elected a new pope who took the Avignon seat, becoming the first of a line of antipopes and beginning the Western Schism.
Avignon school School of late Gothic painting associated with the city of Avignon, Fr., during the Avignon papacy, when many Italian artists worked there. This “school” represents a body of late Gothic painting and not necessarily a single stylistic evolution. Under the direction of Simone Martini, the papal palace of Avignon and secular buildings in nearby towns were decorated with frescoes. The city was one of the channels by which Italian 14th-century art reached France. By the early 15th century Flem¬ ish influences had reached the city, consolidating the Italian and northern styles. The Avignon Pieta (c. 1460), attributed to Enguerrand Charonton,