All articles starting with O
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Osmundastrum
Osmundastrum, cinnamon fern (formerly Osmunda cinnamomea), a monotypic royal-fern genus (Osmundaceae) split from Osmunda on molecular evidence; its single species is an eastern Asia–eastern North America disjunct wetland fern with dimorphic fronds.
Osmundastrum pulchellum
Osmundastrum pulchellum, originally Osmunda pulchella, an extinct royal fern from the Pliensbachian (Lower Jurassic) of Korsaröd, Skåne, Sweden; a probable precursor of modern Osmundastrum known from a permineralized rhizome.
Osnabrück
Osnabrück is a German city in Lower Saxony on the River Hase, founded by Charlemagne in 780, a former Hanseatic town and site of the 1648 Peace of Westphalia, with about 165,000 inhabitants.
Osnova
Osnova (Основа) was a Ukrainian monthly journal of public affairs, literature, and scholarship published in Saint Petersburg from 1861 to 1862, the first Ukrainian periodical in the Russian Empire.
Oso (footballer)
Oso (Joaquín Martínez Gauna, born 2003, Torrevieja) is a Spanish left-footed full-back who broke through at Sevilla in 2025-26 and transferred to RC Strasbourg in August 2026 for €10 million, preferring Argentina internationally.
Oso Ighodaro
Oso Ighodaro (Osasere Benjamin Ighodaro) is an NBA forward/center for the Phoenix Suns, drafted 40th overall in 2024 out of Marquette, where he set the program field goal percentage record (62.4%).
Oso Oil and Gas Field
The Oso Oil and Gas Field is a giant offshore gas condensate field about 12 miles off southeastern Nigeria, discovered in 1967 and producing since 1992.
Osogbo
Osogbo (Oṣogbo, Oshogbo), capital of Osun State, Nigeria, at 7°46′N 4°34′E; a Yoruba commercial city on the Lagos-Kano railway, home of the Ataoja ruler, the Osun-Osogbo Festival, and the UNESCO-listed Sacred Grove.
Osogbo Art School
The Osogbo Art School, also called the Oshogbo School or Osogbo Art Movement, was an informal Nigerian art movement that emerged in Osogbo in the early 1960s.
Osomatsu-kun
Osomatsu-kun (おそ松くん) is Fujio Akatsuka's gag manga about six identical sextuplet brothers, serialized in Weekly Shonen Sunday 1962–1969 and famed for Iyami's "Shee!" fad, adapted as TV anime in 1966, 1988, and as Osomatsu-san in 2015.
Osorkon Bust
The Osorkon Bust is a reddish quartzite bust of the Egyptian pharaoh Osorkon I, dedicated with a Phoenician inscription by Eliba'al, king of Byblos, and held in the Louvre.
Osorkon I
Osorkon I, also known as Sekhemkheperre Osorkon, was the second king of Egypt's Libyan Bubastite 22nd Dynasty and son of Shoshenq I, reigning around 924–889 BC.
Osorkon II
Osorkon II, also known as Usermaatre Osorkon, was a pharaoh of Egypt's Twenty-second Dynasty who reigned from about 874 to 837 BC and built the Sed-festival gateway at Bubastis.
Osorkon II's Sed festival at Bubastis
Osorkon II's Sed festival at Bubastis was the royal jubilee celebrated by pharaoh Osorkon II at the Temple of Bastet, recorded on a granite gateway built for the occasion.
Osorkon IV
Osorkon IV was the last king of Egypt's Twenty-second Dynasty, reigning about 730 to 715 BC over Bubastis and Tanis, and may be the Shilkanni of Assyrian records.
Osorkon the Elder
Osorkon the Elder, throne name Aakheperre and known as Osochor, was a pharaoh of Egypt's 21st Dynasty of Libyan origin in the early 10th century BC.
Osorno
Osorno (Volcán Osorno) is a 2,659-m glaciated stratovolcano in Chile's Los Lagos Region between Lakes Llanquihue and Todos los Santos; last confirmed eruption 1869, sixth on Chile's volcanic risk ranking, dominantly basaltic unlike nearby andesitic Calbuco.
Osowiec Fortress (Крепость Осовец)
Osowiec Fortress (Крепость Осовец, Twierdza Osowiec): Russian Empire fortress in northeastern Poland, built 1882–1892 with four forts on the Biebrza marshes; never captured, it survived three German sieges in WWI including the 1915 gas attack known as the Attack of the Dead Men, and was evacuated in August 1915.
Osoyoos
Osoyoos, British Columbia: a border town on Osoyoos Lake in the South Okanagan, named from the Syilx word soo-yoos. Canada's warmest fresh-water lake, only desert, wine and fruit economy, incorporated 1946, town 1983.
Osp Value
OSP Value is a family of private equity and private credit funds managed by O'Brien-Staley Partners, an investment firm founded in 2010 in Edina, Minnesota.
OSPAR Convention
OSPAR Convention (Convention for the Protection of the Marine Environment of the North-East Atlantic), signed 1992, in force 1998; replaces Oslo 1972 and Paris 1974 conventions; 15 governments plus EU governed by the OSPAR Commission through binding Decisions and non-binding Recommendations.
OSPAR Pipeline
The OSPAR Pipeline (Oleoduto Santa Catarina–Paraná) is a 117 km Brazilian crude oil pipeline running from the São Francisco do Sul terminal to the Repar refinery in Paraná.
Ospedale degli Innocenti
The Ospedale degli Innocenti, or Hospital of the Innocents, is a former foundling hospital in Florence, Italy, begun in 1419 to a design by Filippo Brunelleschi.
Ospemifene
Ospemifene (Osphena, Senshio) is an oral SERM, 60 mg daily with food, for moderate to severe vulvar and vaginal atrophy, dryness, and dyspareunia in postmenopausal women; FDA-approved 2013, EU 2015.
Osphronemus goramy
Osphronemus goramy, the giant gourami (ikan gurami), is a large Southeast Asian labyrinth fish, up to 70 cm SL, farmed for food, an obligate air-breather building plant-fiber nests, IUCN Least Concern.
Ospraie Management, LLC
Ospraie Management, LLC is an American investment management firm founded by Dwight Anderson in 1999 within Tudor Investment Corporation, focused on commodities and basic industry equities.
Osprey
Osprey (Pandion haliaetus), also Western Osprey or fish hawk: a cosmopolitan raptor, sole species of family Pandionidae, feeding almost entirely on live fish caught by feet-first dives; rebounded after the 1972 DDT ban but now faces Chesapeake Bay reproduction declines linked to menhaden.
Osprey optimization algorithm
The osprey optimization algorithm (OOA) is a population-based metaheuristic for continuous and engineering optimization, introduced by Mohammad Dehghani and Pavel Trojovský in 2023, modeling how ospreys hunt fish.
Ospreys (rugby union)
Ospreys (Yr Hebogiaid), Welsh professional rugby union team founded 2003 from Neath RFC and Swansea RFC merger; four league titles, based Swansea, owned by Y11 Sport & Media, moving to St Helen's 2026/27.
OSQP
OSQP (Operator Splitting Quadratic Program) is an open-source numerical optimization package, written in C, that solves convex quadratic programs using the alternating direction method of multipliers.