Organic compound An organic compound is any member of a large class of chemical compounds whose molecules contain carbon and hydrogen; therefore, carbides, carbonates, carbon oxides and chemical element carbon are not organic. The study of organic compounds is termed organic chemistry, and since it is a vast collection of chemicals , systems have been devised to classify organic compounds.
	Organic light-emitting diode An Organic compound light-emitting diode is a special type of light-emitting diode in which the emission layer comprises a thin-film of certain organic compounds. The emissive electroluminescence layer can include a polymer substance that allows the deposition of very suitable organic compounds, for example, in rows and columns on a flat carrier by using a simple "printing" method to create a matrix of pixels which can emit different colour light.
	Organicism Organicism is a Biology doctrine that stresses the organization, rather than the composition, of organisms. William Emerson Ritter coined the term in 1919. Organicism became well-accepted in the 20th century. By definition it is close to holism.
	Organism In biology and ecology, an organism is a life complex system of organ s that influence each other in such a way that they role in some way as a stable whole. An organism is in a non-equilibrium thermodynamics state, maintaining a homeostasis internal natural_environment, and a continuous input of energy is required to maintain this state.
	Organization of American States Organization of American States Organizacin de los Estados Americanos Organisation des tats Amricains Organizao dos Estados Americanos |- | style="background: #ffffff;" align="center" colspan="2" | |- | Headquarters | Washington, D.C.
	Organophosphate An organophosphate is the general name for esters of phosphoric acid and is one of the organophosphorus compounds. They can be found as part of insecticides, herbicides, and nerve gases, amongst others. Some less-toxic organophosphates can be used as solvents, plasticizers, and EP additives.
	Organza Organza is a thin, plain weave, sheer fabric traditionally made from the continuous filament of silkyarn worms. Nowadays though many Organzas are woven with synthetic filament fibers such as polyester or nylon, the most luxurious Organzas are still woven in Silk. Silk Organza is woven by a number of mills along the Yangtzee in China, mainly in the Province of Zhejiang.
	Orgy An orgy is a group activity involving unrestrained indulgence. In contemporary usage, an orgy typically refers to group sex, although it sometimes refers to other activities such as dancing or violence.
	Oriel window Oriel windows are a form of window commonly found in Gothic revival architecture, which jut out from the main wall of the building but do not reach to the ground. Corbels or brackets are often used to support this kind of window. Oriel windows are seen in Arab architecture in the form of mashrabiya.
	Oriental cockroach The Oriental cockroach is a large species of cockroach, measuring about 1 inch in length at maturity. It is dark brown to black in colour and has a glossy body. The female Oriental cockroach has a somewhat different appearance to the male, it appears to be wingless at casual glance but has two very short and useless wings just below its head.
	Oriental Plane The Oriental plane is a very large, widespreading, and long-lived deciduous tree in the Platanaceae family. Its native range includes at least Eurasia from the Balkans to Iran. Some accounts extend its native range to Iberian Peninsula in the west, and to the Himalaya in the east.
	Oriental poppy The Oriental poppy is a perennial poppy of the genus Papaver. Aside from its natural brilliant orange-scarlet, since the later 19th century selective breeding for gardens has created a range of colors from clean white with eggplant-black blotches, through clear true pinks and salmon pinks to a deep maroon.
	Orientalism Orientalism is the study of Near East and Far Eastern societies and cultures, languages and peoples by Western world scholars. It can also refer to the imitation or depiction of aspects of Eastern cultures in the West by writers, designers and artists. In the former meaning the term Orientalism has come to acquire negative connotations in some quarters and is interpreted to refer to the study of the East by Americans and Europeans shaped by the attitudes of the era of European imperialism in the 18th century
	Origami [Image:Pegase.jpg|right|thumb|200px|A paper Pegasus designed by F. Kawahata]] Origami is the art of paper folding. The goal of this art is to create a given result using geometric folds and crease patterns. Origami refers to all types of paper folding, even those of non-Japanese origin.
	Origanum Origanum is a genus of about 20 species of aromatic herbs in the family Lamiaceae, native to the Mediterranean region east to eastern Asia. The genus includes some important culinary herbs, including Marjoram and Oregano. Origanum species are used as food plants by the larvae of some Lepidoptera species including Coleophora.
	Original sin According to Christian tradition, Original sin is the general and non-personal condition of Sin into which human beings are born. It is also called hereditary sin or birth sin. Used with the definite article , it refers to the first sin committed by humans, seen as the seed of future evil effects for the whole human race.
	Originalism In the context of United States constitutional interpretation, originalism is a family of theories which share the starting point that a Constitution has a fixed and knowable meaning which is established at the time of passage or ratification. A neologism, "originalism" is a Legal formalism theory of law, which is closely intertwined with textualism.
	Orinoco The Orinoco is one of the longest rivers in South America at 2,410 km,. Its drainage basin, sometimes called the Orinoquia, covers 880,000 km, 23.7% in Colombia with the rest in Venezuela. The Orinoco and tributaries was, and still is, the major transportation system for eastern and interior Venezuela and the llanos of Columbia.
	ORiNOCO ORiNOCO wireless networking solutions are a family of Lucent chipsets used for Wireless LANs. * White/Bronze labelled Standard WaveLAN IEEE PC Cards * Bronze/Silver labelled WaveLAN IEEE Turbo PC Cards * Silver/Gold labelled WaveLAN IEEE Turbo 11 Mb PC Cards, see Apple AirPort#AirPort "Graphite"
	Orissa Orissa , 60,162 sq mi is a states and territories of India situated in the east coast of India. Orissa is bounded on the north by Jharkhand, on the north-east by West Bengal, on the east by the Bay of Bengal, on the south by Andhra Pradesh and on the west by Chhattisgarh.
	Orizaba Orizaba is a city in the Mexico Mexican state of Veracruz. It is located 20 km west of its sister city Crdoba, Veracruz, and is adjacent to Ro Blanco and Ixtaczoquitln, on Mexican Federal Highway. The name Orizaba comes from a Hispanized pronunciation of the Nahuatl name Ahuilizapan [awil-lis-a-pan], which means "place of playing waters".
	Orkney Islands The Orkney Islands are officially called, and widely known as, simply Orkney. Orkney is one of the 32 council areas of Scotland and consists of about 20 inhabited islands plus 50 others, some quite small, and is 16 km north of Caithness in northern mainland Scotland.
	Orléanais Orl?anais is a former province of France, around the cities of Orl?ans, Chartres, and Blois. The name comes from Orl?ans, its main city and traditional capital. The province was one of those into which France was divided before the French Revolution. It was the country around Orl?ans, the pagus Aurelianensis; it lay on both banks of the Loire River, and for ecclesiastical purposes formed the diocese of Orl?ans.
	Orléans Orlans, is a city and commune in France in north-central France, about 130 km south-west of Paris. It is the prfecture of the Loiret Dpartements of France and of the Centre Rgion in France. Population: 113,126.
	Ormolu Ormolu is an 18th and 19th-century English term for what the French call bronze dor. The modern term in English is gilt bronze though, confusingly, the alloy of copper and zinc, sometimes with an addition of tin is technically brass. The tint of ormolu approximates closely to that of gold; it is heightened by a wash of reddish-gold lacquer, colored with dragon's blood, by immersion in dilute sulphuric acid, or by burnishing.
	Ornithine Ornithine is an amino acid, whose structure is: Ornithine is one of the products of the action of the enzyme arginase on L-arginine, creating urea. Therefore, ornithine is a central part of the urea cycle, which allows for the disposal of excess nitrogen. Ornithine is not an amino acid coded for by DNA, and in that sense, is not involved in protein biosynthesis.
	Ornithischia Ornithischia or Predentata is an order of beaked, herbivore dinosaurs. The name ornithischia is derived from the Ancient Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'. They are known as the 'bird-hipped' dinosaurs because of their bird-like hip structure, even though birds actually descended from the 'lizard-hipped' dinosaurs.
	Ornithopod Ornithopods are a group of ornithischian dinosaurs who started out as small, cursorial grazers, and grew in size and numbers until they became one of the most successful Cretaceous herbivores in the world, and totally dominated the North American landscape. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a reptile, rivaling that of modern mammals like the domestic cow.
	Ornithopter An ornithopter is an aircraft that flies by wing-flapping. Since many examples of wing-flapping flight exist in nature such as birds, bats, and insects, designers of ornithopters seek to imitate this mode of flight. Ornithopters are usually built on the same scale as these flying creatures, though some overscale, manned ornithopters have also been built.
	Ornithorhynchidae Ornithorhynchidae is one of two families in the order Monotreme, and contains the Platypus and its extinct relatives. Within Ornithorhynchidae are two genus, Obdurodon and Ornithorhynchus: *Family Ornithorhynchidae **Genus Obdurodon -- an ancient branch of the platypus family
	Orobanchaceae Orobanchaceae , or the broomrape family, is a family of flowering plants of the order Lamiales, with about 25 genera and more than 200 species. Many of these genera were formerly included in the family Scrophulariaceae s.l. Together they are a monophyletic group, forming a distinct family.
	Orogeny Orogeny is the process of mountain building, and may be studied as a tectonic structural event, as a geographical event and a chronological event, in that orogenic events cause distinctive structural phenomena and related tectonic activity, affect certain regions of rocks and crust and happen within a time frame.
	Orphan An orphan is a person, who has lost one or both parents, often through death. One legal definition used in the USA is someone bereft through "death or disappearance of, abandonment or desertion by, or separation or loss from, of both parents" . Common usage limits the term to children, who have lost both parents.
	Orphenadrine Orphenadrine is a medication used to treat muscle injuries and Parkinson's disease. The citrate salt is most often used for muscle spasms as well as headaches and similar problems, and the hydrochloride is used, often as injection, for Parkinson's disease. At least for the latter use, the citrate and hydrochloride salts are not interchangable.
	Orpheus In Greek mythology, Orpheus was the chief representative of the arts of song and the lyre, and of great importance in the religious history of Greece. The mythical figure of Orpheus was borrowed by the Greeks from their Thracians neighbors; the Thracian "Orphic Mysteries", rituals of unknown content, were named after him.
	Orpiment Orpiment, Arsenic trisulfide, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 C to 325 C . Optically it is biaxial with refractive index of a=2.4, b=2.81, g=3.02.
	Orpington Orpington is a place in the London Borough of Bromley. It is a suburban development located 13.3 miles south east of Charing Cross.
	Orrery An orrery is a mechanical device that illustrates the relative positions and motions of the planets and natural satellites in the solar system in heliocentric model. They are typically driven by a large clockwork mechanism with a globe representing the Sun at the centre, and with a planet at the end of each of the arms.
	Orson Welles George Orson Welles was an United States broadcaster, theatre director, film director and actor. He gained international notoriety for his October 30, 1938 radio broadcast of H. G. Wells' The War of the Worlds , which panicked millions of listeners, but he is best known for his 1941 film classic Citizen Kane, often chosen in polls of film critics as the greatest film ever made.
	Orthoclase Orthoclase is an important igneous rocks forming Silicate minerals mineral. It is also known as alkali feldspar and is common in granite and related rocks. Orthoclase is named based on the Greek language for "straight fracture," because its two cleavages are at right angles to each other.
	Orthodontics Orthodontics is a specialty of dentistry that is concerned with the study and treatment of malocclusions, which may be a result of tooth irregularity, disproportionate jaw relationships, or both. Orthodontic treatment can focus on dental displacement only, or can deal with the control and modification of facial growth.
	Orthoptera The Orthoptera are an order of insects with incomplete metamorphosis, including the grasshoppers, crickets and locusts. Many insects in this order produce sound by rubbing their wings against each other or their legs, the wings or legs containing rows of corrugated bumps.
	Ortolan Bunting The Ortolan, or Ortolan Bunting, Emberiza hortulana, is a bird in the bunting family Emberizidae, a passerine family now separated by most modern authors from the finches, Fringillidae. The bird's common name is French language, from the Latin hortulanus, the gardener bird, .
	Oryx An Oryx is one of three or four large antelope species of the genus Oryx, typically having long straight almost upright horns. Three of the species are found in Africa with a fourth in Arabia and Southern Israel. Small populations exist in Texas and New Mexico, USA.
	Oryzomys The genus Oryzomys contains numerous species of muroid rodents commonly referred to as rice rats. These animals are named due to the prevalence of many species in marshy regions and as pests of rice fields. According to recent phylogenetic analyses, Oryzomys is horribly polyphyletic.
	Osaka listen is the capital of Osaka Prefecture and the third-largest Cities of Japan in Japan, with a population of 2.7 million. It is located in the Kansai region of the main island of Honshu, at the mouth of the Yodo River on Osaka Bay. Osaka is the historical commercial capital of Japan and is still one of Japan's major industrial centers and ports, the heart of the Osaka-Kobe-Kyoto metropolitan area, which has a population of 18,644,000 .
	Osaka Bay Osaka Bay is a bay in western Japan. As an eastern part of the Inland Sea, it is separated from the Pacific Ocean by the Kii Channel and from the neighbor western part of the Inland Sea by the Akashi Strait. Its western shore is formed by Awaji Island, and its northern and eastern shores are part of the Kansai metropolitan area.
	Osama bin Laden Osama bin Muhammad bin 'Awad bin Laden , most commonly known as Osama bin Laden is a militant Islamist and one of the founders of al-Qaeda. Bin Laden issued a 1998 Fatwa that Muslims should kill civilians and military personnel from the United States and allied countries until they withdraw support for Israel and military forces from Islamic countries..
	OSCAR OSCAR is an acronym for Orbital Satellite Carrying Amateur Radio. OSCAR series satellites use amateur radio frequency to communicate with earth. They are conceived, designed, and built by amateur radio operators under the general direction of national organisations such as AMSAT.
	Oscar Hammerstein II :For work done with Richard Rodgers, see Rodgers and Hammerstein Oscar Hammerstein II was an United States writer, producer, and director of musicals for almost forty years. Born in New York City, his father, William, was from a non-practicing Jewish family; his mother, ne Alice Nimmo, was the daughter of Scottish immigrants and their children were raised as Christians.
	Oscar Robertson Oscar Palmer Robertson is a former National Basketball Association player and is considered by many to be one of the greatest basketball players in history. Coaching legend Red Auerbach described Robertson as the most versatile player he had ever seen play. Wilt Chamberlain is quoted to have said "If you don't know the answer to an NBA trivia question, just say 'Oscar Robertson' -- you'll probably be right." To this day, he remains a standard by which other basketball legends are judged.
	Oscar Wilde Oscar Fingal O'Flahertie Wills Wilde was an Anglo-Irish playwright, novelist, Irish poetry, short story writer and Freemason. Known for his barbed and clever wit, he was one of the most successful playwrights of late Victorian Era London, and one of the greatest Celebrity of his day.
	Oscilloscope An oscilloscope is a piece of electronic test equipment that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences plotted as a function of time or of some other voltage . Features and uses Description
	Osculating circle In differential geometry, the osculating circle of a curve at a point shares a common tangent line and a common radius of curvature with the curve at that point. The osculating circle of a mathematically defined curve shares location, first derivative, and second derivative with the curve, just as a tangent line shares location and first derivative.
	Osip Mandelstam Osip Emilyevich Mandelstam was a Russian poet and essayist, one of the foremost members of the Acmeist poetry school of poets.
	Oslo Oslo is the capital and largest city of Norway. The population of the city proper is 544 073 . The city area extends into the surrounding counties of Norway of Akershus, with a total population of 825,105 in the conurbation . The city has a current annual growth exceeding 15,000.
	Osmanthus Osmanthus is a genus of about 30 species of flowering plants in the family Oleaceae, mostly native to warm temperate Asia but one species in North America. They range in size from shrubs to small trees, 2-12 m tall. The leaf are opposite, evergreen, and simple, with an entire, serrated or coarsely toothed margin.
	Osmosis Osmosis is the diffusion of a liquid through a semipermeable membrane from a region of low solvent potential to a region of high solvent potential. The semipermeable membrane must be permeable to the solvent, but not to the solute, resulting in a pressure gradient across the membrane.
	Osmundaceae The Osmundaceae family of ferns is the only family of the order Osmundales, which in turn is the only order in the class Osmundopsida. This is an ancient and fairly isolated group, often known as the "flowering ferns" because of the striking aspect of their ripe sporangia.
	Osprey The Osprey is a medium large bird of prey which is a specialist fish-eater with a worldwide distribution. It is often known by other colloquial names such as fishhawk, seahawk or Fish Eagle. It is the only member of the genus Pandion, which is in turn the only genus in family Pandionidae.
	Ossuary An ossuary is a chest, building, well or site made to serve as the final resting place of human skeleton remains.
	Ostariophysi Ostariophysi is a superorder of fish. Members of this superorder are called ostariophysans. The superorder includes these orders: * Gonorynchiformes * Cypriniformes * Characiformes * Gymnotiformes * Siluriformes
	Osteichthyes Osteichthyes are a taxonomy superclass of fish, also called bony fish that includes the ray-finned fish and lobe finned fish . The Osteichthyes are paraphyletic with land vertebrates, in some classification schemes the tetrapods et al are considered to be members of the Osteichthyes for this reason.
	Osteology Osteology is the science of bones. A subdiscipline of anatomy, osteology is a detailed study of the structure of bones, skeletal elements, teeth, morphology, function, disease, pathology, the process of ossification, the resistance and hardness of bones, etc.
	Osteosarcoma Osteosarcoma is the most common type of malignant bone cancer, accounting for 35% of primary bone malignancies. There is a preference for the metaphysis region of tubular long bones. 50% of cases occur around the knee. It is a malignant connective tissue tumor whose neoplastic cells present osteoblastic differentiation and form tumoral bone.
	Osteostraci Class Osteostraci, once known as "Ostracoderma," was a group of bony-armored jawless fish that lived in what is now North America, Europe and Russia from the Wenlock epoch to Late Devonian. Anatomically speaking, the osteostracans, especially the Devonian species, were among the most advanced of all known agnathans.
	Ostracod Ostracoda is a Class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 50,000 extinct and extant species have been identified, grouped into several orders. Ostracods are small crustaceans, typically around one mm in size, but varying between 0.2 to 30 mm, laterally compressed and protected by a bivalve-like, chitinous or calcareous valve or "shell".
	Ostrava Ostrava is the third largest city in the Czech Republic and the administrative center of the Moravian-Silesian Region. It is located at the confluence of the Ostravice, Oder river and Opava rivers. Its history and growth have been largely affected by exploitation and further usage of the high quality black coal deposits discovered in the locality, giving the town a look of an industrial city and a nickname of the steel heart of the republic during the communism of Czechoslovakia
	Ostrich The ostrich is a flightless bird native to Africa. It is the only living species of its family , Struthionidae, and its genus, Struthio. They are distinct in their appearance, with a long neck and legs and the ability to run at speeds of about 65 km/h .
	Ostrich fern The Ostrich fern is a crown-forming, colony-forming fern, occurring in temperate regions of the Northern Hemisphere in eastern and northern Europe, northern Asia and northern North America. It grows from a completely vertical crown, favoring riverbanks and sandbars, but sends out lateral stolons to form new crowns.