| The Columbia Encyclopedia, Sixth Edition. 2001-07. |
| |
| |
| Ono to Orkney Islands |
| |
| Ono |
| onomatopoeia |
| Onomichi |
| Onondaga |
| Onondaga Lake |
| Ono no Komachi |
| Onslow, George |
| Ontario, province, Canada |
| Ontario, city, United States |
| Ontario, Lake |
| ontogeny |
| ontology |
| O Nuallaian, Brian |
| Onychophora |
| onyx |
| oolite |
| Oomycota |
| Oort, Jan Hendrik |
| Oort cloud |
| Oost, Jacob van |
| Oostende |
| Ootacamund |
| OPA |
| opal |
| Opalinida |
| Opa-Locka |
| op art |
| Opava |
| OPEC |
| Opelika |
| Opelousas |
| open-chain compound |
| open cluster |
| Open Door |
| open education |
| open-end investment company |
| open enrollment |
| open-hearth process |
| open shop |
| Open University |
| Opéra |
| opera |
| opera glass |
| operational amplifier |
| operetta |
| operon |
| Ophel |
| Ophelia |
| ophicleide |
| Ophion |
| Ophir |
| Ophites |
| Ophrah |
| ophthalmia neonatorum |
| ophthalmology |
| ophthalmoscope |
| Ophüls, Marcel |
| Ophüls, Max |
| opiate drug |
| Opie, John |
| Opitz, Martin |
| opium |
| Opium Wars |
| Opobo |
| Opole |
| Oporto |
| opossum |
| Oppeln |
| Oppenheimer, J. Robert |
| Opper, Frederick Burr |
| Oppian |
| Oppland |
| Opportunity |
| opportunity school |
| opposition |
| Ops |
| optative |
| optical activity |
| optical character recognition |
| optical density |
| optical disk |
| optical double |
| optical rotation |
| optical sensing |
| optician |
| optic nerve |
| optics |
| optometry |
| opus |
| Opus Dei |
| oracle |
| oracle bones |
| Oradea |
| Öraefajökull |
| Oraibi |
| Oral |
| oral history |
| Oran |
| Orange, town, France |
| Orange, cities, United States |
| orange, in botany |
| Orangeburg |
| Orange Free State |
| Orangemen |
| Orange River |
| orangutan |
| Oranienbaum |
| Oranienburg |
| Oranjestad |
| oratorio |
| oratory |
| Oratory, Congregation of the |
| orbit |
| Orbiting Astronomical Observatory |
| Orbiting Geophysical Observatory |
| Orbiting Solar Observatory |
| Orcagna |
| orchard |
| orchard grass |
| orchestra and orchestration |
| orchid |
| orchil |
| Orchomenus |
| Ord, Edward Otho Cresap |
| ordeal |
| order |
| Ordericus Vitalis |
| Order of American Knights |
| orders, holy |
| orders in council |
| orders of architecture |
| Ordinance of 1787 |
| ordinate |
| ordination |
| Ordos |
| Ordovician period |
| Ordu |
| Ordzhonikidze |
| ore |
| oread |
| Oreb |
| Örebro |
| oregano |
| Oregon, state, United States |
| Oregon, city, United States |
| Oregon, University of |
| Oregon Caves National Monument |
| Oregon grape |
| Oregon State University |
| Oregon Trail |
| Orekhovo-Zuyevo |
| Orel |
| Orellana, Francisco de |
| Orem |
| Ore Mountains |
| Orenburg |
| Orense |
| Oreopithecus |
| Oreor |
| Orestes, Roman general |
| Orestes, in Greek mythology |
| Orestia |
| Øresund |
| Orff, Carl |
| Orford, Robert Walpole, 1st earl of |
| organ |
| organic chemistry |
| organic farming |
| organic food |
| Organization for Economic Cooperation and Development |
| Organization for Security and Cooperation in Europe |
| Organization of African Unity |
| Organization of American States |
| Organization of Petroleum Exporting Countries |
| organized crime |
| organometallic chemistry |
| Organ Pipe Cactus National Monument |
| organ transplant |
| organum |
| Orhan |
| Oribe, Manuel |
| oribi |
| oriel |
| Orientale |
| orientation |
| Origen |
| original sin |
| Orillia |
| Orinoco |
| oriole |
| Orion, in Greek mythology |
| Orion, in astronomy |
| Orion Nebula |
| Orissa |
| Oriya |
| Orizaba, city, Mexico |
| Orizaba, mountain, Mexico |
| Orkhan |
| Orkhon |
| Orkney Islands |
|
|
| |
|
| | | The Columbia Encyclopedia, Sixth Edition. Copyright © 2007 Columbia University Press. |
|
|
