Encyclopædia Britannica Australia -

Encyclopedias since 1768

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Ontario ... operetta

Ontario: second largest province of Canada in area. It occupies the strip of the Canadian mainland lying between Hudson and James bays on the north and the St. Lawrence River-Great Lakes chain to the south. It is bordered to the east ...
Ontario Science Centre: in Toronto, Ont., Can., a science and technology museum. Founded in 1964, the centre offers major collections in aeronautics, agriculture, anatomy, botany, mineralogy, textiles, and other areas. It also makes available to the public an aquarium, arboretum, outdoor exhibits, and ...
Ontario, Lake: smallest and most easterly of the Great Lakes of North America. It is bounded on the north by Ontario (Can.) and on the south by New York (U.S.). The lake is roughly elliptical; its major axis, 193 miles (311 km) ...
ontology: the theory or study of being as such; i.e., of the basic characteristics of all reality. Though the term was first coined in the 17th century, ontology is synonymous with metaphysics or "first philosophy" as defined by Aristotle in the ...
Onverwacht series: division of Archean rocks (the Archean Eon lasted from 3.96 to 2.5 billion years ago) in the Swaziland region of southern Africa. The Onverwacht series is well known from exposures in the Komati valley in the eastern Transvaal region, South ...
onyx: striped, semiprecious variety of the silica mineral agate with white and black alternating bands. Onyx is used in carved cameos and intaglios because its layers can be cut to show a colour contrast between the design and the background. Other ...
Oodnadatta: town, northern South Australia. It lies on the Neales River, southwest of the Simpson Desert. Founded in 1890, Oodnadatta served as the northern terminus of the Central Australian Railway (until the railway was extended to Alice Springs some 280 miles ...
oogenesis: in the human female reproductive system, growth process in which the primary egg cell (or ovum) becomes a mature ovum. In any one human generation, the egg's development starts before the female that carries it is even born; 8 to ...
Ooka Makoto: prolific Japanese poet and literary critic who was largely responsible for bringing contemporary Japanese poetry to the attention of the Western world.
Ooka Shohei: Japanese novelist famous for his depiction of the fate of Japanese soldiers during World War II.
Ooka Tadasuke: highly respected Japanese judge of the Tokugawa period (1603-1867).
oolite: ovoid or spherical crystalline deposit with a concentric or radial structure; most are composed of calcium carbonate, but some are composed of silica, siderite, calcium phosphate, iron silicate, or iron oxide. Oolite diameters range from 0.25 to 2 mm (0.01 ...
Oomycetes: class of fungi (kingdom Fungi) distinguished by their production of asexual reproductive cells, called zoospores, that can move through the use of one or two whiplike swimming structures (flagella). New fungi may germinate from these spores, or mature fungi may ...
Oort cloud: immense, roughly spherical cloud of icy small bodies that are inferred to revolve around the Sun at distances typically more than 1,000 times that of the orbit of Pluto, the outermost known planet. Named for the Dutch astronomer Jan Oort, ...
Oort, Jan Hendrik: Dutch astronomer who was one of the most important figures in 20th-century efforts to understand the nature of the Milky Way Galaxy.
ooze: pelagic (deep-sea) sediment of which at least 30 percent is composed of the skeletal remains of microscopic floating organisms. Oozes are basically deposits of soft mud on the ocean floor. They form on areas of the seafloor distant enough from ...
Op art: branch of mid-20th-century geometric, abstract art that deals with optical illusion. Achieved through the systematic and precise manipulation of shapes and colours, the effects of Op art can be based either on perspective illusion or on chromatic tension; in painting, ...
opah: large marine fish of the family Lampridae (order Lampridiformes), widely distributed in warm oceans. A deep-bodied fish with a small, toothless mouth, the opah grows to a length of about 2 m (7 feet) and a weight of 140 kg ...
opal: silica mineral extensively used as a gemstone, a submicrocrystalline variety of cristobalite (q.v.). In ancient times opal was included among the noble gems and was ranked second only to emerald by the Romans. In the Middle Ages it was supposed ...
opaline glass: usually opaque glass or crystal, either white or coloured, made in France between approximately 1810 and 1890. Opaline resembles the milk glass of 16th-century Venice and the opaque, white glass associated with Bristol, Eng., in the 18th century.
opalinid: (subphylum Opalinata), any of about 150 protozoans found in the intestinal tracts of amphibians and some other animals. The nuclei of opalinids vary in number from two (e.g., Zelleriella) to many (e.g., Cepedea); the locomotor organelles (short, hairlike projections) are ...
Opalinski, Krzysztof: Polish statesman and writer who was a noted satirist.
Oparin, Aleksandr: Russian biochemist noted for his studies on the origin of life from chemical matter. By drawing on the insights of chemistry, he extended the Darwinian theory of evolution backward in time to explain how simple organic and inorganic materials might ...
Opatija: resort town, one of the best-known coastal resorts in Istria, republic of Croatia, situated on the Kvarner (gulf) of the Adriatic Sea. The town's name derives from the old Benedictine opatija ("abbey") of San Giacomo al Palo, situated in the ...
Opava: city, Severomoravsky kraj (region), eastern Czech Republic. It lies along the Opava River near the Polish border and is northwest of Ostrava, from which it is separated by part of the wooded Oder Hills.
OPEC: multinational organization that was established to coordinate the petroleum policies of its members and to provide member states with technical and economic aid.
Opel AG: German automotive company, a wholly owned subsidiary of the U.S. General Motors Corporation, specializing in the manufacture of passenger cars, minibuses, and light vans. Headquarters are in Russelsheim, Ger.
Opel, Fritz von: German automotive industrialist who took part, with Max Valier and Friedrich Wilhelm Sander, in experiments with rocket propulsion for automobiles and aircraft.
Opelika: city, seat (1866) of Lee county, eastern Alabama, U.S. It is situated about 15 miles (24 km) west of the Chattahoochee River, adjacent to Auburn.
Opelousas: city, seat (1805) of St. Landry parish, south-central Louisiana, U.S. It lies on the Gulf Coastal Plain, 20 miles (32 km) north of Lafayette. Founded in 1720 as a French garrison and trading post and named for the Opelousas Indians, ...
open cluster: in astronomy, any group of young stars held together by mutual gravitation. See star cluster.
Open Door policy: statement of principles initiated by the United States (1899, 1900) for the protection of equal privileges among nations trading with China and in support of Chinese territorial and administrative integrity. The statement was issued in the form of circular notes ...
Open Range: in U.S. history, the areas of public domain north of Texas where from about 1866 to 1890 more than 5,000,000 cattle were driven to fatten and be shipped off to slaughter. The open ranges of western Kansas, Nebraska, the Dakotas, ...
open stage: theatrical stage without a proscenium, projecting into the audience and surrounded on three sides by the audience. The open stage was used in the corrales of Spain's Golden Age of theatre (beginning about 1570) and in the traditional no theatre ...
Open University: British experiment in higher education for adults. It opened in January 1971 with headquarters at the new town of Milton Keynes, Buckinghamshire. There are no academic prerequisites for enrollment in Open University, the aim of which is to extend educational ...
open-field system: basic community organization of cultivation in European agriculture for 2,000 years or more. Its best-known medieval form consisted of three elements: individual peasant holdings in the form of strips scattered among the different fields; crop rotation; and common grazing. Crop ...
open-heart surgery: any surgical procedure that requires an incision into the heart, exposing one or more of the cardiac chambers. The most common open-heart operations are for repair of valvular disease and for correction of congenital heart defects, chiefly septal and valve ...
open-hearth process: steelmaking technique that for most of the 20th century accounted for the major part of all steel made in the world. William Siemens, a German living in England in the 1860s, seeking a means of increasing the temperature in a ...
open-market operation: any of the purchases and sales of government securities and sometimes commercial paper by the central banking authority for the purpose of regulating the money supply and credit conditions on a continuous basis. Open-market operations can also be used to ...
open-pit mining: surface mining (q.v.) to obtain minerals other than coal.
open-source software: computer software whose source code is put into the public domain, subject to the restriction that any improvements or derived software also include the source code and be put into the public domain.
opencast mining: surface mining (q.v.) to obtain minerals other than coal.
Opera: Paris opera house designed by Charles Garnier. The building, considered one of the masterpieces of the Second Empire style, was begun in 1861 and opened with an orchestral concert on Jan. 5, 1875. The first opera performed there was Fromental ...
opera: a drama set to music and made up of vocal pieces with orchestral accompaniment and with orchestral overtures and interludes. In some operas, such as those by Richard Wagner, the music is continuous throughout an act; in others, it is ...
opera buffa: (Italian: "comic opera"), genre of comic opera originating in Naples in the mid-18th century. It developed from the intermezzi, or interludes, performed between the acts of serious operas. Opera buffa plots centre on two groups of characters: a comic group ...
opera seria: (Italian: "serious opera"), style of Italian opera dominant in 18th-century Europe. It emerged in the late 17th century, notably in the work of Alessandro Scarlatti and other composers working in Naples, and is thus frequently called Neapolitan opera. The primary ...
opera-comique: French form of opera in which spoken dialogue alternates with self-contained musical numbers. The earliest examples of opera-comique were satiric comedies with interpolated songs, but the form later developed into serious musical drama distinguished from other opera only by its ...
operating system: program that manages a computer's resources, especially the allocation of those resources among other programs. Typical resources include the central processing unit (CPU), computer memory, file storage, input/output (I/O) devices, and network connections. Management tasks include scheduling resource use to ...
operations research: application of scientific methods to the management and administration of organized military, governmental, commercial, and industrial processes.
operator: in mathematics, any symbol that indicates an operation to be performed. Examples are x (which indicates the square root is to be taken) and ddx (which indicates differentiation with respect to x is to be performed). An operator may be ...
operetta: musical-dramatic production similar in structure to an opera but characteristically having a romantically sentimental plot interspersed with songs, orchestral music, and rather elaborate dancing scenes, along with the spoken dialogue. The operetta originated in part with the tradition of popular ...