| Original proof of Gödel's completeness theorem | Orca | Organic electronics |
| Orson WellesCarl Van Vechten, 1937 George Orson Welles ( May 6, 1915 October 10, 1985) is commonly considered one of Hollywood's greatest directors, as well as a fine actor and screenwriter. Early career Welles was born in Kenosha, Wisconsin. He had an unusual childh | OregonOregon is a state located in the western United States bordering the Pacific Ocean, California, Washington, Idaho, and Nevada. Its northern border lies along the Columbia River and the east along the Snake River. Two north-south mountain ranges the Coasta | OrbitalThe term orbital has several meanings: in physics it is used to describe an atomic electron configuration, see also molecular orbital in physiology it is used to describe the region of the skull in which the eyeball is located in space exploration "going |
| Organic compoundAn organic compound is any of a large class of chemical compounds whose molecules contain carbon, with exception of carbides, carbonates and carbon oxides. Organic compounds are studied in organic chemistry; many of them, such as proteins, fats, and carbo | Organic chemistryOrganic chemistry is the scientific study of the structure, properties, composition, reactions, and synthesis of organic compounds. Organic nomenclature Organic nomenclature is the system established for naming and grouping organic compounds. Aliphatic co | OrthographyThe orthography of a language is the set of rules of how to write correctly in the language. The term is derived from Greek omicron;ρθ&omicron ortho ("correct") and gamma;ραφο&sigmaf graphos ("that writes") and, in today's |
| OrdovicianThe Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. The Ordovician follows the Cambrian period and is followed by the Silurian period. The Ordovician named after the Welsh tribe of the Ordovices was define | OreganoOregano Origanum vulgare is a spicy, Mediterranean, perennial herb, particularly common in Greek and Italian cuisines. It is the leaves that are used in cooking, and the dried herb is often more flavourful than the fresh. Classification Oregano (also call | OregonianAn Oregonian is a resident or native of the state of Oregon; The Oregonian is the daily newspaper in Portland. Oregon. |
| Orkhon script | Orkhon inscriptions | Orrorin |
| Ordered pair | Ordinal number | Organ |
| Organometallic compound | Organelle | Orson Scott Card |
| Order automorphism | Orange | Ordered field |
| Oracle machine | Orangutan | Orbital resonance |
| Organic nomenclature | Orion | Orsini family |
| Orhan I | Orbit | Orthodox Judaism |
| Orienteering | Organometallic chemistry | Orient House |
| Oracle | Oracle Corporation | Organization |
| Ore | Orlando Letelier | Organism |
| Oral contraceptive | Organized crime | Orkney Islands |
| Orders of magnitude | Orimulsion | Organization of the Communist Party of the USSR |
| Oromo | Oral history | Orthogonal frequency division modulation |
| Origin of life | Oriental Orthodoxy | Origen |
| Orchestra | Origin | Orchidaceae |
| Original sin | Order of the Eastern Star | Orthodox Bahá'í Faith |
| Original Amiga chipset | Organization of American States | Organization for Security and Co-operation in Europe |
| Ordinary English | Orange Alternative | Orgy of the Dead |
| Organizers of the September 11, 2001 attacks | Organisation for the Prohibition of Chemical Weapons | Orientalism |
| Orlando Bloom | Orbital revolution | Orientalium Ecclesiarum |
| Ornithology | Orc | Organ donation |
| Orem, Utah | Orange County | Orange County, California |
| Orpheus in the Underworld | Orchestration | Organization of the Islamic Conference |
| Orleans (disambiguation) | Organisation of African Unity | Oregon Trail |
| Organ Pipes National Park | Orange County, Texas | Original Dixieland Jass Band |
| Origami | Orange juice | Order |
| Orogeny | Ortler, Oetzthal and Stubai Ranges | Oresund |
| Orleans County, New York | Orange County, New York | Oral glucose tolerance test |
| Ordeal in Space | Orange Book | Orrery |
| Ortolan Bunting | Oral law | Order (biology) |
| Organisation de l'Armée Secrète | Oravita | Oradour-sur-Glane |
