All articles starting with O

Orthoflavivirus denguei

Orthoflavivirus denguei (dengue virus) is the ICTV-accepted flavivirus species containing the four dengue serotypes DENV-1 to DENV-4, positive-sense ssRNA viruses of Flaviviridae spread by Aedes mosquitoes.

Orthoflavivirus flavi

Orthoflavivirus flavi is the ICTV species for yellow fever virus (YFV), a mosquito-borne positive-sense RNA flavivirus of Africa and South America causing hemorrhagic fever, prevented by the lifelong-protective 17D vaccine.

Orthoflavivirus japonicum

Orthoflavivirus japonicum, the Japanese encephalitis virus (JEV), is a mosquito-borne Orthoflavivirus species causing Asia's main viral encephalitis; renamed from Japanese encephalitis virus by ICTV in 2023; ~100,000 cases yearly, Culex-borne, vaccine-preventable.

Orthoglide

The Orthoglide is a three-degree-of-freedom translational parallel manipulator with three orthogonal linear joints and a mobile platform of fixed orientation, designed at IRCCyN in Nantes, France, beginning in 2001 for rapid machining.

Orthognathic surgery

Orthognathic surgery, or corrective jaw surgery, surgically repositions the mandible, maxilla, or both via Le Fort I, BSSO, and genioplasty to treat malocclusion, facial asymmetry, and sleep apnea, combined with orthodontics.

Orthogonal array

An orthogonal array, introduced by C. R. Rao in the 1940s, is a table of symbols in which every chosen set of columns contains all combinations equally often.

Orthogonal array design

Orthogonal array design is a design of experiments method using orthogonal arrays to estimate all main effects uncorrelatedly from relatively few test runs, widely used in industrial quality engineering.

Orthogonal collocation

Orthogonal collocation is a numerical method for solving differential equations by expanding the solution in orthogonal polynomials and forcing the equation to hold at their roots, introduced by Villadsen and Stewart in 1967.

Orthogonal complement

The orthogonal complement of a subset U of an inner product space is the set of all vectors whose inner product with every vector of U is zero.

Orthogonal coordinates

Orthogonal coordinates are a coordinate system in which coordinate lines or surfaces intersect at right angles, a common case of curvilinear coordinates including Cartesian, cylindrical, and spherical systems.

Orthogonal experimental design

Orthogonal experimental design is a design-of-experiments method that arranges factor levels in orthogonal arrays, estimating each factor's effects independently with far fewer runs than a full factorial experiment.

Orthogonal frequency-division multiple access

Orthogonal frequency-division multiple access (OFDMA) is a multicarrier scheme that assigns groups of subcarriers to different users, serving as the LTE downlink and a defining feature of Wi-Fi 6.

Orthogonal frequency-division multiplexing

Orthogonal frequency-division multiplexing (OFDM), also called discrete multitone modulation, is a multicarrier modulation technique that splits data across many orthogonal subcarriers, dominant in Wi-Fi, LTE, 5G, and digital television.

Orthogonal group

The orthogonal group, or general orthogonal group, is the classical group of linear transformations preserving a non-singular quadratic form; O(n) consists of the real orthogonal matrices preserving distances in n-dimensional Euclidean space.

Orthogonal iteration

Orthogonal iteration, also called subspace iteration or simultaneous iteration, is a numerical linear algebra algorithm that generalizes the power method to compute bases for eigenspaces.

Orthogonal matching pursuit

Orthogonal matching pursuit (OMP) is a greedy algorithm for sparse approximation, introduced by Mallat and Zhang in 1993, which recovers sparse signals from fewer measurements than the signal dimension.

Orthogonal matrix

An orthogonal matrix, also called an orthonormal matrix, is a real square matrix whose transpose equals its inverse; it preserves lengths and angles, representing a rotation, a reflection, or both.

Orthogonal partial least squares

Orthogonal partial least squares (O-PLS) is a multivariate regression method that separates variation correlated with a response from uncorrelated variation, introduced by Trygg and Wold in 2002.

Orthogonal polynomials

Orthogonal polynomials are sequences of polynomials whose distinct members are orthogonal under a weighted inner product; introduced by Legendre in 1783, they underlie Gaussian quadrature, quantum mechanics, and approximation theory.

Orthogonal projection

Orthogonal (orthographic) projection is a drafting method that represents a three-dimensional object by projecting its edges onto perpendicular planes along parallel projectors, producing the standard views of engineering drawings.

Orthogonal protecting groups and deprotection strategy

Orthogonal protecting groups are masking groups on one molecule, each removable selectively under conditions that leave all the others intact, a concept defined by Barany and Merrifield in 1977.

Orthogonal time frequency space modulation

Orthogonal time frequency space (OTFS) modulation is a digital modulation scheme for wireless communication, introduced in 2017, that places symbols on a delay-Doppler grid and outperforms OFDM at high speeds.

Orthogonality

Orthogonality is the generalization of perpendicularity to inner product spaces, where two elements are orthogonal when their inner product is zero; it underlies Fourier series and least squares.

Orthographic map projection

The orthographic map projection, also called the orthographic projection in cartography, is an azimuthal perspective projection that shows one hemisphere as a globe appears from space.

Orthographic projection

Orthographic projection, also called orthogonal projection, is a parallel projection method for representing three-dimensional objects in two dimensions, the primary method used in engineering drawings of manufactured parts.

Orthography

Orthography: the accepted spelling rules of a language, distinct from script. Covers orthographic depth (shallow Italian vs. deep English), reading acquisition, dyslexia measurement, and Unicode guidance for new orthographies.

Oct 20, 2026

Orthograptus

Orthograptus Lapworth 1873 is an extinct Ordovician biserial (scandent) diplograptid graptolite genus, planktonic and suspension-feeding, best known through the O. quadrimucronatus species group.

Orthohantavirus

Orthohantavirus is a genus of rodent-borne, negative-sense RNA viruses (family Hantaviridae, about 60 species) causing HFRS in Eurasia and hantavirus cardiopulmonary syndrome in the Americas; Hantaan virus, its prototype, was isolated in 1976.