All articles starting with O

Oprah with Meghan and Harry

Oprah with Meghan and Harry: A CBS Primetime Special, also called the Sussex Oprah interview, was Oprah Winfrey's March 7, 2021 two-hour CBS interview with the Duke and Duchess of Sussex, watched by 17.1 million Americans, covering racism allegations and their royal exit.

Oprah's Book Club

Oprah's Book Club, also called the Oprah Winfrey Book Club, is Winfrey's personally curated book-selection franchise launched in 1996 on The Oprah Winfrey Show, now under Oprah Daily and Apple TV+, with 125 picks and a documented million-copy-per-selection sales effect.

Oprelvekin

Oprelvekin (Neumega), recombinant human interleukin-11, was the first FDA-approved drug (1997) for chemotherapy-induced thrombocytopenia; withdrawn from the US market for fluid retention, arrhythmias, and cost.

Sep 24, 2026

Oprichniki

The Oprichniki (опричники) were the black-clad armed corps sworn to Tsar Ivan the Terrible, created in 1565 to terrorize suspected traitors and abolished with the oprichnina in 1572.

Oprichnina

Oprichnina (Опричнина), from Old Russian "separate": Tsar Ivan IV's personal appanage and associated policy in Muscovy, 1565-1572, with its own army (oprichniki), a parallel zemshchina, terror against the boyars, the 1570 sack of Novgorod, and abolition in 1572.

Sep 24, 2026

Oprichnina Court

The Oprichnina Court (Опричный двор) was the personal court and armed retinue of Tsar Ivan IV of Russia, created in 1565 and abolished in 1572.

Sep 24, 2026

Oprichnina decree of 1565

The Oprichnina decree of 1565 (Учреждение опричнины 1565 года) was the act by which Tsar Ivan IV divided Muscovy into his personal oprichnina and the zemshchina.

OPRL1

OPRL1 is the human gene on chromosome 20 encoding the NOP (ORL1, OP4) nociceptin receptor, the fourth opioid-family GPCR, activated by the 17-amino-acid peptide nociceptin/orphanin FQ and insensitive to morphine and naloxone.

Opryland USA

Opryland USA, a country music-themed amusement park in Nashville, Tennessee, operated 1972 to 1997 before closing for the Opry Mills mall; its rides were sold to Premier Parks.

Ops

Ops, Roman goddess of abundance and riches (Latin ops, "plenty"); festivals Opiconsivia (25 August) and Opalia (19 December) tied to Consus; wife of Saturn only after Hellenism; not originally agrarian per Miano 2015.

Ops Corona

Ops Corona is a named corona on Venus at 68.5N, 89.0E, a quasi-circular volcano-tectonic feature with concentric fracture annulus; IAU name approved 1991 for a Greek fertility goddess.

Oct 15, 2026

OPS-SAT

OPS-SAT was a 3U CubeSat of the European Space Agency launched in December 2019 as an in-orbit laboratory for testing mission control techniques, ending with atmospheric reentry in May 2024.

Opsin

Opsin: light-sensitive seven-transmembrane GPCR apoprotein that binds retinal via a Schiff base; forms rhodopsin and visual pigments (Type II animal opsins), distinct from Type I microbial opsins used in optogenetics.

Opsismodysplasia

Opsismodysplasia (OPSMD, OMIM 258480) is a rare autosomal recessive skeletal dysplasia with severely delayed bone ossification, short limbs, small hands and feet, and characteristic facial features; biallelic INPPL1 variants explain about 60% of cases.

Opsoclonus-myoclonus syndrome

Opsoclonus-myoclonus syndrome (Kinsbourne syndrome, dancing eye syndrome) is a rare neuroinflammatory disorder with opsoclonus, myoclonus, ataxia, and sleep and behavioral disturbance, usually paraneoplastic from neuroblastoma in children and lung or breast cancer in adults.

Sep 29, 2026

Opsonophagocytic killing assay

The opsonophagocytic killing assay (OPKA) is an in vitro immunology assay measuring how antibodies and complement enable phagocytes to kill bacteria, used to evaluate functional immunity from bacterial vaccines.

Opština Vraneštica

Opština Vraneštica (Вранештица) was a small former municipality in western North Macedonia, seat at Vraneštica village; 109.13 km², 15 settlements, 1,322 inhabitants (2002), merged into Kičevo municipality in 2013.

OPT (Meta model family)

OPT (Open Pre-trained Transformer) is a family of language models released by Meta AI in May 2022, with sizes from 125 million to 175 billion parameters, roughly matching GPT-3.

OPT-175B

OPT-175B is a 175-billion-parameter language model built by Meta AI like GPT-3 and released to researchers in May 2022 with training code and a complete training logbook.

Opt-outs in the European Union

Opt-outs in the European Union are treaty-based exemptions letting member states stay outside specific EU policies, notably Denmark's four Maastricht opt-outs (euro, defense, citizenship, justice) and the UK's EMU, Social Protocol, and Schengen exemptions.

Optatiana

Optatiana: Roman auxiliary fort and vicus at Sutor, Sălaj County, Romania, in Dacia Porolissensis, on the Tabula Peutingeriana; garrisoned by the numerus Maurorum Optatianensium, a Moorish cavalry unit of about 500 men.

Opteron

Opteron, or AMD Opteron, is a family of x86 server processors from AMD, introduced in 2003 as the first 64-bit processor compatible with the x86 architecture.

Optic atrophy

Optic atrophy, better termed optic neuropathy, is death of retinal ganglion cell axons causing a pale optic disc and vision loss; causes include glaucoma, compression, ischemia, toxins, and inherited mitochondrial disorders like LHON and OPA1-related dominant optic atrophy.

Optic atrophy 3-like

Optic atrophy 3-like is a conserved protein family of small mitochondrial membrane proteins homologous to human OPA3, found from yeast and plants to fish and mammals.

Optic atrophy-intellectual disability syndrome

Optic atrophy-intellectual disability syndrome, or Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS, OMIM 615722), is a rare autosomal dominant NR2F1 disorder with developmental delay, intellectual disability, optic atrophy, hypotonia, and seizures.

Optic axis of a crystal

The optic axis of a crystal, or extraordinary axis, is the direction along which light travels without double refraction; uniaxial crystals have one, biaxial two.

Optic chiasm

Optic chiasm: brain-base structure where optic nerves partially decussate, nasal retinal fibers crossing (about 53:47 crossed-to-uncrossed), enabling binocular vision; pituitary tumor compression causes bitemporal hemianopia.

Optic disc

Optic disc (optic nerve head): retinal site where ganglion cell axons exit as the optic nerve; no photoreceptors, so it forms the blind spot; central retinal vessels pass through it; key glaucoma and papilledema landmark.

Optic disc dysplasia

Optic disc dysplasia (ICD-11 LA13.73) is a congenital malformation in which the optic disc is deformed and fits no recognized diagnostic category; related excavated anomalies include morning glory disc anomaly, optic disc pit, and coloboma, with risks of retinal detachment and systemic associations such as papillorenal syndrome.