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 varieties include carnelian onyx, with white and

marble: The so-called onyx marbles consist of concentric zones of calcite or aragonite deposited from cold-water solutions in caves and crevices and around the exits of springs. They are, in the strict sense, neither marble nor onyx, for true onyx is a banded chalcedony composed largely of silicon…

Antarctica: Relief: The evanescent Onyx River, for example, flows from Lower Wright Glacier terminus to empty into the nondrained basin of Lake Vanda near McMurdo Sound. Glacially sculptured landforms now predominate, as they must have some 300 million years ago, in an earlier period of continental glaciation of all…

Kortrijk: The Church of Notre Dame (Onze Lieve Vrouwkerk; 1191–1211), with the attached chapel of the counts of Flanders (1374), contains Anthony Van Dyck’s “Elevation of the Cross” (1631) and a 14th-century statue of St. Catherine. Other historic landmarks in Kortrijk include the Broelbrug (bridge; c. 1400),…

Paulo Coelho: The Alchemist and other works: …humankind; and Onze minutos (2003; Eleven Minutes), which explores the boundaries between love and sex through the story of a prostitute. A bruxa de Portobello (2006; The Witch of Portobello) tells the story of a female religious leader in the form of interviews with those who knew her. O vencedor…

protist: Reproduction and life cycles: …highly resistant stage—for example, the oocyst of the coccidian parasites, which may survive for a long time in the fecal material of the host or in the soil. This cyst is the infective stage for the next host in the parasite’s life cycle.

animal development: Preparatory events: …or egg), derived from an oocyte (immature egg), and the male sex cell (spermatozoon or sperm), derived from a spermatocyte. Eggs are produced in ovaries; sperm, in testes. Both the egg and the sperm contribute to the development of the new individual; each providing one set of genes, thereby restoring…

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 [450 km] north-northwest in 1929),

gamete: …advanced form of heterogamy called oogamy. In oogamy one of the gametes is small and motile (the sperm), and the other is large and nonmotile (the egg).

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 20 weeks after the fetus has started to grow, cells that

archegonium, the female reproductive organ in ferns and mosses. An archegonium also occurs in some gymnosperms, e.g., cycads and conifers. A flask-shaped structure, it consists of a neck, with one or more layers of cells, and a swollen base—the venter—which contains the egg. Neck-canal cells,

sedimentary rock: …or siliceous shell fragments and oöids, which are concentrically layered spherical grains of calcium carbonate. Orthochemical sedimentary rocks, on the other hand, consist of dissolved constituents that are directly precipitated as solid sedimentary rock and thus do not undergo transportation. Orthochemical sedimentary rocks include some limestones, bedded evaporite deposits of…

Ōoka Makoto was a prolific Japanese poet and literary critic who was largely responsible for bringing contemporary Japanese poetry to the attention of the Western world. The son of a tanka poet, Ōoka graduated from the University of Tokyo in 1953 with a degree in literature and subsequently worked

Ōoka Shōhei was a Japanese novelist famous for his depiction of the fate of Japanese soldiers during World War II, in which he served. He was also known for his insightful commentary on human behavior, as well as his carefully crafted prose and graceful literary style. Novelist Ōe Kenzaburō, who

Ōoka Tadasuke was a highly respected Japanese judge of the Tokugawa period (1603–1867). Appointed to office by Tokugawa Yoshimune (shogun 1716–45), Ōoka soon gained a reputation as one of the most able and incorruptible officials of the realm. As a reward, Yoshimune also appointed him the head of a

malaria: The course of the disease: …gametocytes produces embryonic forms called ookinetes; these embed themselves in the mosquito’s gut, where they mature after 9 to 14 days into oocysts, which in turn break open and release thousands of sporozoites that migrate to the insect’s salivary glands, ready to infect the next person in the cycle.

oölite, 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. Oölite diameters range from 0.25 to 2 mm (0.01 to 0.08 inch), with most being in

mineral deposit: Iron deposits: …of an iron mineral), these oolitic iron deposits have been largely supplanted in importance by BIFs, but they once formed the backbone of the iron and steel industries in western Europe and North America. European oolitic iron deposits, commonly called Minette-type deposits, contain ooliths of siderite, a siliceous iron mineral…

oolong, tea of Chinese origin, made from partially oxidized tea leaves. It therefore falls between a black tea (which is fully oxidized) and a green tea (which is barely oxidized). Known in China as oōlióng(dé), meaning “black dragon (tea),” oolong holds an intermediate position on the spectrum of

André Philippus Brink: …oomblik in die wind (1975; An Instant in the Wind), and Gerugte van reën (1978; Rumours of Rain) used the sexual relationship between a black man and a white woman to show the destructiveness of racial hatred. Brink was perhaps best known outside his homeland for the antiapartheid novel ’N…

Oomycota, phylum of funguslike organisms in the kingdom Chromista. Oomycetes may occur as saprotrophs (living on decayed matter) or as parasites living on higher plants and can be aquatic, amphibious, or terrestrial. The species Phytophthora infestans famously destroyed Ireland’s potato crop with

Eve Queler: …Queler founded in 1971 the Opera Orchestra of New York, which also provided experience to instrumentalists and young singers. Their performances of Claudio Monteverdi’s L’incoronazione di Poppea and Ottorino Respighi’s Belfagor in 1971, Gioacchino Rossini’s William Tell and Giacomo Meyerbeer’s L’Africana in 1972, and other works established the orchestra

the Mekons: …their significant later releases were OOOH! (Out of Our Heads) (2002), Natural (2007), Ancient & Modern (2011), and Existentialism (2017), the last of which captures a live experimental performance in Brooklyn featuring just-written politically charged songs.

object-oriented programming, use of predefined programming modular units (objects, classes, subclasses, and so forth) in order to make programming faster and easier to maintain. Object-oriented languages help to manage complexity in large programs. Objects package data and the operations on them so

mumps: …breasts (mastitis) or ovaries (oophoritis) in females, and, rarely, involvement of the pancreas, but these are of short duration and usually of no serious significance. The testicles may become atrophied, but sterility from this cause is uncommon. Meningoencephalitis (inflammation of the brain and its membranous covering) is a fairly…

three-parent baby: Mitochondrial replacement therapy: Ooplasmic transfer entails the injection of a small amount of cytoplasm from an egg cell (ovum) donated by a healthy woman into the mother’s egg, which is then fertilized by the father’s sperm and implanted into the mother’s uterus using IVF. Because ooplasmic transfer involves…

Britney Spears: Princess of Pop: …Baby One More Time, Oops!…I Did It Again, and In the Zone: …she released her second album, Oops!…I Did It Again. It sold 1.3 million copies in its first week of release, setting a record for first-week sales by a solo artist. Although Spears drew criticism for her revealing attire—often imitated by her female fans—she was able to convey a wholesomeness that…

Jim Thorpe: …two seasons (1922–23) with the Oorang Indians, whose owner attracted crowds by having Thorpe and his teammates dress up and perform “Indian” tricks before games and at halftime. In 1920–21 he served as the first president of the American Professional Football Association (later the National Football League [NFL]). He also…

Kolar Gold Fields: …years, four main veins (Champion, Oorgaum, Nundydorog, and Mysore) were opened. Champion, the deepest, reached some 10,500 feet (3,200 metres) below sea level.

Khoekhoe: …Khoekhoe are either Nama or Orlams, the latter term denoting remnants of the “Cape Hottentots” together with many of mixed ancestry. The main Nama groups are the Bondelswart, Rooinasie, Zwartbooi, and Topnaar; the main Orlams groups are the Witbooi, Amraal, Berseba, and Bethanie. The Khoekhoe are not physically distinguishable from…

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 Neptune, the outermost known major planet. Named for the Dutch astronomer Jan Oort, who demonstrated its existence, the Oort

Milky Way Galaxy: Rotation: …2l, where A is called Oort’s constant and is approximately 15 km/sec/kiloparsec (1 kiloparsec is 3,260 light-years), r is the distance to the star, and l is the galactic longitude.

Jan Oort was a Dutch astronomer who was one of the most important figures in 20th-century efforts to understand the nature of the Milky Way Galaxy. After studies at the University of Groningen, Oort was appointed astronomer to the Leiden Observatory in 1924. In 1935 he was appointed professor at

Jan Oort was a Dutch astronomer who was one of the most important figures in 20th-century efforts to understand the nature of the Milky Way Galaxy. After studies at the University of Groningen, Oort was appointed astronomer to the Leiden Observatory in 1924. In 1935 he was appointed professor at

Jan Oort was a Dutch astronomer who was one of the most important figures in 20th-century efforts to understand the nature of the Milky Way Galaxy. After studies at the University of Groningen, Oort was appointed astronomer to the Leiden Observatory in 1924. In 1935 he was appointed professor at

East London, port city, Eastern Cape province, South Africa. It lies at the mouth of the Buffalo River along the Indian Ocean. Buffalo Harbour, first visited by the British in 1836 and named Port Rex, was used as a supply base during the seventh Cape Frontier War (1846). The next year, Fort

seed: Gymnosperm seeds: …organs) develop, each containing an oosphere (“egg”). The pollen tube ultimately penetrates the neck of one of the archegonia. Not until the second growing season, however, does the nucleus of one of the male cells in the tube unite with the oosphere nucleus. Although more than one archegonium may be…

algae: Evolution and paleontology of algae: The oospore, the fertilized female egg, has spirals on its surface that were imprinted by the spiraling protective cells that surrounded the oospore. Oospores from before about 225 million years ago had right-handed spirals, whereas those formed since that time have had left-handed spirals. The reason…

Belgium: (West Flanders, East Flanders [West-Vlaanderen, Oost-Vlaanderen], Flemish Brabant, Antwerp, and Limburg). Just north of the boundary between Walloon Brabant (Brabant Walloon) and Flemish (Vlaams) Brabant lies the officially bilingual but majority French-speaking Brussels-Capital

IJsselmeer Polders: …[469 square km]), and the East (Oostelijk) Flevoland Polder (204 square miles [528 square km]) were completed in 1930, 1942, and 1957, respectively. The South (Zuidelijk) Flevoland Polder (166 square miles [430 square km]) was completed in 1968. A fifth potential polder is the Markerwaard Polder in southwest IJsselmeer. Under…

Ostend, municipality, Flanders Region, northwestern Belgium. It lies along the North Sea and at the end of the Ghent-Brugge Canal. A fishing village (originally Oostende-ter-Streepe) since the 9th century, it was fortified in 1583 and became the last Dutch stronghold in Belgium, falling to the

Bennie Oosterbaan was an American collegiate football player and coach for the University of Michigan (Ann Arbor), who was the first of the great collegiate pass receivers. His coaching record was 63 games won, 33 lost, and 4 tied. In his first year as coach his team won nine games and lost none

Bennie Oosterbaan was an American collegiate football player and coach for the University of Michigan (Ann Arbor), who was the first of the great collegiate pass receivers. His coaching record was 63 games won, 33 lost, and 4 tied. In his first year as coach his team won nine games and lost none

Bilderberg Meetings: …name from the hotel at Oosterbeek, Netherlands, where the first conference was held in 1954. An international steering committee generally selects different delegates each year.

Eastern Schelde, channel extending about 50 km (30 miles) northwestward through the Delta Islands in the southwestern Netherlands to the North Sea. A former estuary of the Schelde River (as well as of the Meuse [Maas] River before completion in 1970 of a dam on the Volkerak Channel), the Eastern

Eastern Schelde: …the Delta Works project, the Oosterscheldedam (Eastern Schelde Dam) at the mouth of the channel is a storm surge barrier that has transformed the channel into a tidal saltwater area. Secondary dams include the Oesterdam in the eastern part of the Eastern Schelde and the Philipsdam in the Volkerak Channel…

Udhagamandalam, town, western Tamil Nadu state, southern India. It is situated in the Nilgiri Hills at an elevation of about 7,500 feet (2,300 meters) above sea level and is sheltered by several peaks—including Doda Betta (8,652 feet [2,637 meters]), the highest point in Tamil Nadu. It was founded

Calhoun, city, seat of Gordon county, northwestern Georgia, U.S. It lies near the Oostanaula River, 21 miles (34 km) northeast of Rome. Known formerly as Oothcaloga (“Place of the Beaver Dams”) and, later, as Dawsonville, the town was renamed in 1850 to honour the South Carolina statesman John C.

insect: Egg: …cemented together to form an egg packet or ootheca. Insects may pass unfavourable seasons in the egg stage. Eggs of the springtail Sminthurus (Collembola) and of some grasshoppers (Orthoptera) pass summer droughts in a dry shrivelled state and resume development when moistened. Most eggs, however, retain their water although they…

Udhagamandalam, town, western Tamil Nadu state, southern India. It is situated in the Nilgiri Hills at an elevation of about 7,500 feet (2,300 meters) above sea level and is sheltered by several peaks—including Doda Betta (8,652 feet [2,637 meters]), the highest point in Tamil Nadu. It was founded

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 land so that the slow but steady deposition of

elephant: Importance to humans: Mahouts and oozies (elephant trainers in India and Myanmar, respectively) are skilled people who remain in direct contact with the animals for many years. The handlers take care of all the elephants’ needs, and the bond between man and beast becomes very strong. Hastividyarama, an…

Convention on the Elimination of All Forms of Discrimination Against Women: …30 articles and includes an optional protocol (OP). Human rights agreements often include OPs to provide an alternative mechanism to hold governments accountable or to further elaborate on any substantive topic within the treaty itself. In the case of CEDAW, the OP consists of the Communications Procedure, which enables people…

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 colors, the effects of Op art can be based either on perspective illusion or on chromatic tension; in painting, the dominant medium of

Burgess Shale: …down its plated back; and Opabinia, which had five eyes and a long nozzle, have led many scientists to conclude that the Cambrian Period may have produced many unique phyla. However, deposits discovered in China, Greenland, and elsewhere have demonstrated that at least some of the shale’s oddities (including Hallucigenia…

library: Vehicles for catalogs: …is known as OPAC (on-line public access computer). Further development of this system has made it possible to integrate other library records with the OPAC, so that patrons can reserve materials that are still on order and can determine if items in the library’s collection are already on loan.…

industrial glass: Transparency, opacity, and colour: Because electrons in glass molecules are confined to particular energy levels, they cannot absorb and reemit photons (the basic units of light energy) by skipping from one energy band to another and back again. As a consequence, light energy travels through glass…

opah, (genus Lampris), any of two species of large marine fish of the family Lampridae (order Lampridiformes). One species, Lampris guttatus, is the only known fully warm-blooded fish. Although two species are recognized traditionally, some classifications suggest that anatomical evidence exists to

opah: One species, Lampris guttatus, is the only known fully warm-blooded fish. Although two species are recognized traditionally, some classifications suggest that anatomical evidence exists to divide L. guttatus into five species.

opal, silica mineral extensively used as a gemstone, a submicrocrystalline variety of cristobalite. 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 to be lucky, but in modern times it has been regarded

industrial glass: Silica-based: …not transparent product known as opal glass can be obtained. Another silica-based variation is borosilicate glass, which is used where high thermal shock resistance and high chemical durability are desired—as in chemical glassware and automobile headlamps. In the past, leaded “crystal” tableware was made of glass containing high amounts of…

coloration: Short-term changes: Greenfish, or opaleye (Girella nigricans), kept in white-walled aquariums became very pale during a four-month period, storing about four times the quantity of integumentary guanine as was recoverable from the skins of individuals living in black-walled aquariums but receiving the same kind and amounts of…

Ops: …dating of her festivals (the Opalia on December 19 and the Opiconsiva on August 25) illustrate her affinities with the Saturnalia (December 17) and the Consualia (of Consus; December 15).

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 arranged in

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. The main centres of production were

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 arranged in

Krzysztof Opaliński was a Polish statesman and writer who was a noted satirist. A highly educated and well-traveled man, and governor (wojewoda) of the province of Poznań, Opaliński figured in the history of Polish literature as the author of Satyry albo przestrogi do naprawy rządu i obyczajów w

ironstone china, type of stoneware introduced in England early in the 19th century by Staffordshire potters who sought to develop a porcelain substitute that could be mass-produced. The result of their experiments was a dense, hard, durable stoneware that came to be known by several names—e.g.,

cereal processing: Corn: These corns, called Opaque-2 and Floury-2, possess certain drawbacks. They are generally lower in yield than dent hybrids, are subject to more kernel damage when combine-harvested, and may be more difficult to process. Nevertheless, these new hybrid corns are expected to become widely cultivated, and the principles involved…

Aleksandr Oparin was a 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 have combined into complex

Aleksandr Oparin was a 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 have combined into complex

Oparin-Haldane theory, idea that organic molecules could be formed from abiogenic materials in the presence of an external energy source—e.g., ultraviolet radiation—and that Earth’s primitive atmosphere was reducing (having very low amounts of free oxygen) and contained ammonia and water vapour,

northern Mexican Indian: …Taracahitic group, the once prominent Ópata, have lost their own language and no longer maintain a separate identity. The Piman languages are spoken by four groups: the Pima Bajo of the Sierra Madre border of Sonora–Chihuahua; the Pima-Papago (O’odham) of northwest Sonora, who are identical with a much larger portion…

Opatija, resort town, one of the best-known coastal resorts in Istria, western Croatia. It is situated at the head of the Kvarner, a gulf of the Adriatic Sea along the eastern side of the Istrian peninsula. The town’s name derives from the old Benedictine opatija (“abbey”) of San Giacomo al Palo,

Opava, city, northeastern 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. First recorded as Oppavia in 1195, it was a principate and fief of the Bohemian crown in the early 14th century

Opava, city, northeastern 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. First recorded as Oppavia in 1195, it was a principate and fief of the Bohemian crown in the early 14th century

torture: Contemporary developments: In 2002 the Optional Protocol to the Convention against Torture (OPCAT) established a Subcommittee on Prevention, an expert body that, unlike the committees and the Special Rapporteur, would have the right and obligation to visit states without further consent of a state party to the protocol. Inspired by…

Organisation for the Prohibition of Chemical Weapons (OPCW), international organization established by the Chemical Weapons Convention (adopted 1992, entered into force 1997) to implement and enforce the terms of the international treaty, which prohibits the use, stockpiling, or transfer of

optics: Seidel sums: …is generally called OPD, meaning optical path difference. It can be shown that OPD is related to x0 and y0 by five constants S1 through S5, and the quantity h′o,Each of these five terms is considered to be a separate “aberration,” the coefficients S1

Ottoman Empire: The 1875–78 crisis: …and a European-controlled organization, the Ottoman Public Debt Administration (OPDA), was set up to collect the payments.

mangabey: …subspecies of the black mangabey, Opdenbosch’s mangabey (L. aterrimus opdenboschi) has a shorter crest, and the thick straight cheek whiskers are black like the body; it is confined to a few gallery forests on the rivers south of the Congo. The kipunji (Rungwecebus kipunji) was initially placed in the genus…

Abiy Ahmed: Entry into politics: …as a member of the Oromo People’s Democratic Organization (OPDO), which was part of the Ethiopian People’s Revolutionary Democratic Front (EPRDF) ruling coalition. In the following years he would go on to earn a master’s degree in transformational leadership (2011) from the International Leadership Institute in Addis Ababa, in partnership…

OPEC, multinational organization that was established to coordinate the petroleum policies of its members and to provide member states with technical and economic aid. OPEC was established at a conference held in Baghdad September 10–14, 1960, and was formally constituted in January 1961 by five

Native American: The mid-Atlantic Algonquians: …1618 his brother and successor, Opechancanough, attempted to force the colonists out of the region. His men initiated synchronized attacks against Jamestown and its outlying plantations on the morning of March 22, 1622. The colonists were caught unawares, and, having killed some 350 of the 1,200 English, Opechancanough’s well-organized operation…

Opel AG, German automotive company, a wholly owned subsidiary of Stellantis NV, specializing in the manufacture of passenger cars and light vans. Its headquarters are in Rüsselsheim, Germany. The company was started in 1898 when the five Opel brothers began converting the bicycle and sewing machine

Fritz von Opel was a German automotive industrialist who took part, with Max Valier and Friedrich Wilhelm Sander, in experiments with rocket propulsion for automobiles and aircraft. He was a grandson of Adam Opel, who in 1862 had founded at Rüsselsheim a firm bearing his name that manufactured

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. The first settlers entered the area following the signing of a final treaty with the Creek in 1832. Opelika is a Creek word meaning “large

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, it became a sanctuary for Acadians exiled from Nova

museum: Early period of reassessment: …museums at Arnhem, Netherlands (Netherlands Open Air Museum; opened 1912), and at St. Fagans, Wales (the Museum of Welsh Life; opened as the Welsh Folk Museum in 1948). The preservation and restoration of buildings or entire settlements in situ also began; particularly well known is Colonial Williamsburg, founded in…

airport: Open apron and linear designs: …for passenger terminals is the open apron design, in which aircraft park on the apron immediately adjacent to the terminal and passengers walk across the apron to board the aircraft by mobile steps. Frequently, the aircraft maneuver in and out of the parking positions under their own power. As airports…

Netscape Communications Corp.: Browser enhancements: …expanded Navigator’s capabilities; this “open-architecture” approach led in particular to a proliferation of plug-ins for digital audio, video, and animation. Netscape was among the first licensees of Sun Microsystems, Inc.’s Java programming language and virtual-machine technology. Sun and Netscape also collaborated to define JavaScript, a separate language designed to…

breed association: …registered; this is called an open association. The qualifications may be type, colour, or speed. Standardbred horses, for example, are admitted to the registry if they can trot a mile in 2 minutes 30 seconds, or pace a mile in 2 minutes 25 seconds. Older associations generally require that each…

The Open Boat, short story by Stephen Crane, published in the collection The Open Boat and Other Tales of Adventure in 1898. It recounts the efforts of four survivors of a shipwreck—a newspaper correspondent and the ship’s cook, captain, and oiler—as they attempt to remain afloat in a dinghy on

Plymouth Brethren: …Exclusive Brethren; the others, called Open Brethren, maintained a congregational form of church government and less rigorous standards for membership. Exclusive Brethren have suffered further divisions.

caisson: An open caisson, open at both the bottom and the top, is fitted with a cutting bottom edge, which facilitates sinking through soft material while excavation is carried out inside through a honeycomb of large pipes, or dredging wells. As excavating proceeds and the caisson sinks,…

freight car: …since the early 1800s: the open-top car, the boxcar, and the flatcar.

British Open, one of the world’s four major golf tournaments—with the Masters Tournament, the U.S. Open, and the PGA Championship—and the oldest continually run championship in the sport. Best known outside the United States as the Open Championship or, simply, the Open, it has been held annually

animal: Water/vascular systems: Most animals have open circulatory systems. Those few animals with closed circulatory systems have a continuous series of vessels to circulate fluid to the vicinity of all cells, whereas those with open systems have vessels only near the heart. (Actually, no system is entirely closed or open.) In…

Open City, Italian Neorealist film, released in 1945, that portrayed life in Nazi-occupied Rome during World War II. Directed by Roberto Rossellini in a documentary style that was innovative for the time, the movie brought international attention to the Neorealist movement and became one of its

free school, school in which the teaching system is based on an environment structured to encourage the child to become actively involved in the learning process. The free school stresses individualized rather than group instruction, and children proceed from one step to another at their own rate