All articles starting with O

Open map

An open map is a function between topological spaces that sends every open set to an open set; every homeomorphism is open, and non-constant holomorphic functions are open maps.

Open mapping theorem (functional analysis)

The open mapping theorem, or Banach–Schauder theorem, is a functional analysis result stating that every surjective bounded linear operator between Banach spaces sends open sets to open sets.

Open market operation

An open market operation (OMO) is a central bank's purchase or sale of securities to manage the supply of reserves and steer short-term interest rates.

Open marriage: a married couple's mutual agreement permitting sexual, sometimes emotional, relationships outside the marriage; a form of consensual non-monogamy popularized by the O'Neills' 1972 book, distinct from infidelity, swinging, and polyamory.

Open mic

Open mic (open microphone): recurring public events where anyone performs music, comedy, poetry, or storytelling without a formal booking, via sign-up slots of a few minutes; distinct from jam sessions, rooted in radio, folk coffeehouses, and comedy clubs.

Open Mobile Alliance

The Open Mobile Alliance (OMA) is a non-profit standards organization formed in June 2002 by nearly 200 mobile companies, publishing open service-layer specifications for mobile and IoT interoperability.

Open Networking Foundation

The Open Networking Foundation (ONF) was an operator-led nonprofit consortium, founded in 2011 to advance software-defined networking through OpenFlow and open standards; it dissolved in December 2023, moving its projects to the Linux Foundation.

Open pancreaticoduodenectomy

Open pancreaticoduodenectomy, the Whipple procedure, is an operation through a laparotomy that removes the pancreatic head and duodenum, mainly to treat pancreatic head and periampullary tumors.

Open peer review

Open peer review (OPR) is an umbrella term for transparent peer review models, including open identities, open reports, and open participation; a systematic review found 122 definitions, and 617 journals practiced some form by 2019.

Open plan

An open plan is a floor layout where kitchen, dining, and living rooms flow together without walls, popularized by modernist architecture after World War II.

Open Platform Communications

Open Platform Communications (OPC), originally OLE for Process Control, is a series of open standards for secure data exchange in industrial automation, first released in 1996 and maintained by the OPC Foundation.

Open pollination

Open pollination is pollination within a cultivar by self- or cross-pollination rather than a controlled cross, yielding genetically diverse open-pollinated varieties whose seed stays true-to-type when isolated.

Open pond cultivation

Open pond cultivation is the large-scale growth of photosynthetic microorganisms, chiefly microalgae and cyanobacteria, in shallow open-air raceway ponds whose low cost makes them the basis of industrial algal biofuel production.

Open post-training reproduction efforts (Open-R1)

Open-R1 is a Hugging Face project launched in January 2025 to reconstruct the missing training data and pipeline behind DeepSeek-R1, whose weights were open but whose recipe was not.

Open primaries in the United States

Open primaries in the United States let any registered voter choose a party's primary ballot privately without party registration. Covers NCSL primary types, state lists, top-two and top-four variants, turnout and polarization research, and 2024-2025 reform outcomes.

Open prison

Open prison (minimum security prison): a penal institution where prisoners serve sentences without being locked up, focused on resettlement. Category D in England and Wales; widely used in Norway; lower cost and generally lower recidivism than closed prisons.

Oct 22, 2026

Open Quantum Materials Database

The Open Quantum Materials Database (OQMD) is a free database of density functional theory calculations on inorganic materials, maintained by the Wolverton group at Northwestern University.

Open RAN

Open RAN is a cellular network architecture in which the radio access network is built from disaggregated, virtualized multivendor components connected through open interfaces, replacing single-supplier systems.

Open Range (2003 film)

Open Range (2003) is a Western directed by and starring Kevin Costner with Robert Duvall, based on Lauran Paine's novel The Open Range Men. Free grazers fight a rancher in 1882; released August 15, 2003, grossing $58.3 million.

Oct 22, 2026

Open Reaction Database

The Open Reaction Database (ORD) is an open-access repository and schema for organic reaction data, begun in 2019 to support machine learning for reaction prediction and synthesis planning.

Open reading frame

Open reading frame (ORF): a DNA or RNA stretch read as codons from an initiator codon to a stop codon, central to gene finding; six reading frames per double-stranded segment; short ORFs encode microproteins.

Open reduction of fractures

Open reduction of fractures is a surgical procedure in which a fractured bone is exposed so fragments can be directly realigned, often combined with plate-and-screw internal fixation as ORIF.

Open relationship

Open relationship: a committed relationship in which partners agree one or both may have sex (sometimes romance) with others; a form of consensual non-monogamy alongside polyamory and swinging, distinguished from infidelity by consent and affecting about 4-5% of partnered adults.

Open rhinoplasty

Open rhinoplasty is a surgical technique for reshaping the nose in which the skin is lifted through an external incision across the columella, exposing the cartilage and bone directly.

Open Road Films

Open Road Films is an American independent film distributor founded in 2011 by AMC and Regal, sold to Tang Media Partners in 2017, bankrupt in 2018, and owned since 2019 by Raven Capital Management; it released Spotlight, the 2016 Best Picture Oscar winner.