All articles starting with O

Orthobunyavirus

Orthobunyavirus: largest genus of Peribunyaviridae, tripartite negative-sense RNA viruses with four structural proteins, spread by mosquitoes and midges; includes La Crosse, Bunyamwera, and Oropouche viruses.

Orthobunyavirus oropoucheense

Orthobunyavirus oropoucheense (Oropouche virus, OROV, "sloth fever") is a segmented RNA virus of Peribunyaviridae causing Oropouche fever, spread by Culicoides paraensis midges in the Amazon basin and, since late 2023, across the Americas.

Orthobunyavirus schmallenbergense

Orthobunyavirus schmallenbergense (Schmallenberg virus, SBV), a Simbu serogroup orthobunyavirus of ruminants transmitted by Culicoides midges, emerged near Schmallenberg, Germany in 2011, causing congenital malformations in calves and lambs and major EU trade losses.

Orthocarbonate esters

Orthocarbonate esters are organic compounds of general formula C(OR)₄, the stable tetraesters of hypothetical orthocarbonic acid C(OH)₄, with tetramethyl and tetraethyl orthocarbonate the best known.

Orthocarbonic acid

Orthocarbonic acid, also called methanetetrol, is the hypothetical compound C(OH)₄, first detected in the gas phase in 2025 in laboratory simulations of interstellar ice chemistry.

Orthocenter

The orthocenter of a triangle is the point where its three altitudes meet, lying inside an acute triangle, outside an obtuse one, and at the right-angle vertex itself.

Orthoceras

Orthoceras (Bruguière, 1789) is a genus of straight-shelled orthocerid cephalopods, restricted to the type species O. regulare from the Middle Ordovician of Baltoscandia; the name is widely misapplied to Moroccan trade fossils and Triassic forms now placed in Trematoceras.

Orthoclase

Orthoclase, also called orthoclase feldspar, is a rock-forming potassium feldspar mineral with the formula KAlSi₃O₈, common in granite and named in 1823 for its right-angle cleavage.

Orthodontic Anchorage Procedures

Orthodontic anchorage procedures (orthodontic anchorage techniques) attach devices in the mouth to resist unwanted tooth movement, ranging from headgear and transpalatal arches to titanium miniscrews and miniplates, with miniscrew failure rates around 13.5%.

Orthodontic Appliance Design

Orthodontic Appliance Design: planning and creation of devices to straighten teeth, spanning Andrews' straight-wire brackets, functional appliances, clear aligners, and CAD/CAM and FEA design methods.

Orthodontic Appliances

Orthodontic appliances (braces, aligners, functional appliances, retainers) are devices for influencing tooth position, classified as fixed or removable, active or retaining, intraoral or extraoral; from Fauchard's 1728 bandolet to Invisalign.

Sep 29, 2026

Orthodontic extrusion

Orthodontic extrusion, also called forced eruption, is an orthodontic technique that slowly moves a tooth out of its socket to expose fractured or subgingival structure for restoration.

Orthodontic Retainers

Orthodontic retainers (fixed bonded wires, Hawley, clear vacuum-formed) hold teeth after braces; relapse affects over half of patients at 10 years without retention.

Orthodontic Space Closure

Orthodontic space closure is the orthodontic procedure of closing gaps between teeth, usually premolar extraction sites, using sliding or loop mechanics to move teeth along an archwire.

Sep 29, 2026

Orthodontic space maintenance

Orthodontic space maintenance, or space maintenance, uses fixed or removable appliances to hold the gap left by a prematurely lost primary tooth until the permanent tooth erupts.

Orthodontic Wires

Orthodontic wires, chiefly arch wires, are the force-delivering backbone of fixed braces. Evolved from gold alloy through stainless steel to superelastic and heat-activated nickel-titanium, beta-titanium, and aesthetic or bactericide wires.

Orthodontics

Orthodontics: dental specialty treating malocclusions (misaligned teeth and bites) with braces and clear aligners. About a third of children need treatment; courses last 12 months to 2.5 years; aligners suit mild-to-moderate cases, fixed appliances complex ones.

Orthodontists

Orthodontists are dental specialists trained to correct malocclusions with fixed braces or clear aligners. Also called orthodontic specialists; the largest US dental specialty, about 5% of dentists, with documented treatment risks and heavy education debt.

Orthodox Church in America

The Orthodox Church in America is a self-governing Eastern Orthodox church based in the United States, granted autocephaly by the Moscow Patriarchate in 1970, though several churches, notably Constantinople, have not recognized it.

Sep 24, 2026

Orthodox Church in the Grand Duchy of Lithuania

The Orthodox Church in the Grand Duchy of Lithuania (Prawosławna Cerkiew w Wielkim Księstwie Litewskim) served the state's Orthodox population from the early 14th century until 1795.

Orthodox Church of Ukraine (Православна церква України)

The Orthodox Church of Ukraine (Православна церква України) is an autocephalous Eastern Orthodox church covering Ukraine. Created in December 2018 by uniting two Ukrainian churches, it is headed by Metropolitan Epifaniy, seated in Kyiv.

Orthodox Judaism

Orthodox Judaism is the branch of Judaism that holds the Torah and halakha to be divinely given and fully binding, arising in Europe in the late 1700s.

Oct 22, 2026

Orthodox Party

The Orthodox Party (Partido del Pueblo Cubano – Ortodoxos) was a Cuban populist political party founded by Eduardo Chibás in 1947 to fight government corruption; Batista's 1952 coup ended the elections it was favored to win.

Oct 22, 2026

Orthodox school (Chinese painting)

The orthodox school (正统派) of Chinese painting was the early Qing landscape tradition of the Four Wangs, favored by the imperial court and dominant into the twentieth century.

Orthodox stance

The orthodox stance is the standard fighting position in boxing, with the left foot and hand leading so the dominant right hand throws power punches; about 90% of boxers use it.

Orthodox Study Bible

The Orthodox Study Bible is a one-volume English study Bible for Eastern Orthodox Christians, published in 2008 with a Septuagint Old Testament and New King James Version New Testament.

Orthodox Tewahedo biblical canon

The Orthodox Tewahedo biblical canon, also called the Ethiopian Bible, is the broadest Christian canon, counting 81 books, including Enoch, Jubilees, and the Meqabyan books unique to it.

Orthodoxy (ὀρθόδοξος)

Orthodoxy, from Greek ὀρθόδοξος meaning "right belief", is conformity to an authoritative norm of doctrine, opposed to heterodoxy, and the name of the Eastern Orthodox churches.

Orthodoxy or death!

Orthodoxy or death! (Greek Ορθοδοξία ή θάνατος; Russian Православие или смерть) is an ethno-religious motto from Mount Athos's Esphigmenou monastery, spread by Russian conservatives and far-right groups, litigated in Russia, and disavowed by Patriarch Kirill.