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Subspace Pursuit
Subspace Pursuit is an iterative greedy algorithm for reconstructing sparse signals from compressed measurements, proposed by Wei Dai and Olgica Milenkovic and published in IEEE Transactions on Information Theory in 2009.
Subspace theorem
The Subspace theorem is a 1972 result of Wolfgang M. Schmidt in Diophantine approximation, generalizing Roth's theorem: solutions of a product inequality in linear forms lie in finitely many subspaces.
Subspace topology
The subspace topology, also called the induced or relative topology, is the topology on a subset A of a space X whose open sets are the intersections U ∩ A.
Subspecies
Subspecies: taxonomic rank below species, named with a trinomen (e.g., Puma concolor coryi), for geographic or morphologically distinct populations not reproductively isolated; contested rank with proposed 75% and diagnosability criteria, used in conservation listings.
Subspecies of Canis lupus
Subspecies of Canis lupus: named geographic populations of the gray wolf, historically 32 worldwide (24 in North America), with genetics validating some, such as the Mexican wolf C. l. baileyi, and leaving North American designations unsettled.
Substack
Substack is a San Francisco subscription publishing platform founded in 2017 by Chris Best, Hamish McKenzie, and Jairaj Sethi. It takes 10% of subscription revenue, passed 5 million paid subscriptions in March 2025, and reached a $1.1 billion valuation in July 2025.
Substance 1987
Substance 1987 is New Order's first compilation album, released by Factory Records (FACT 200) in August 1987; it collects the band's 12-inch singles and B-sides, peaked at UK number 3, and sold over one million copies.
Substance abuse
Substance abuse, now diagnosed as substance use disorder under DSM-5, is compulsive use of alcohol or drugs despite harm. Covers neurobiology, 40-60% genetic risk, US prevalence, overdose trends, NPS monitoring, and treatments.
Substance abuse detection
Substance abuse detection, also called drug abuse screening, is the set of clinical methods for identifying drug or alcohol misuse through questionnaires, laboratory testing, and electronic health record analysis.
Substance dependence
Substance dependence, also called physical dependence, is a state in which the body needs a drug to function, marked by tolerance and withdrawal; distinct from addiction (substance use disorder), treatable with tapering and FDA-approved medications.
Substance intoxication
Substance intoxication, also called getting high, is a reversible syndrome of disturbed consciousness, perception, and behavior after recent use of alcohol or another psychoactive substance.
Substance over form
Substance over form is an accounting principle requiring transactions to be accounted for by their economic substance and financial reality, not merely their legal form.
Substance P
Substance P (SP) is an 11-amino acid tachykinin neuropeptide, discovered 1931 by von Euler and Gaddum, sequenced 1971, signaling mainly through the NK1 receptor; its antagonists treat chemotherapy-induced nausea.
Substance Painter
Substance Painter is a 3D painting application, created by Allegorithmic and acquired by Adobe in 2019, used to texture and render 3D meshes with real-time PBR feedback.
Substance theory
Substance theory, or substance ontology, is the metaphysical view that reality's fundamental constituents are substances. Contrasts with bundle theory, substratum theory, hylomorphism, and Whiteheadian process ontology; rooted in Aristotle's Categories.
Substance use & misuse
Substance Use & Misuse (Subst Use Misuse) is a peer-reviewed Taylor & Francis journal on drugs, alcohol, nicotine, and eating disorders; founded 1996, continuing the International Journal of the Addictions (1966–1995), ISSN 1082-6084, indexed in MEDLINE.
Substance use disorder
Substance use disorder (SUD), also called drug addiction, is a DSM-5-TR diagnosis of impaired control over alcohol or drug use, mild to severe by criteria count; 44.6 million US cases in 2025, 11% treated.
Substantia gelatinosa of Rolando
Substantia gelatinosa of Rolando (SGR), or substantia gelatinosa, is the translucent lamina II of the spinal dorsal horn, described by Rolando in 1824, that receives C and Aδ fiber input and modulates nociception via gate control circuitry.
Substantia nigra
The substantia nigra, Latin for "black substance", is a nucleus of the midbrain that supplies dopamine to the basal ganglia and helps modulate motor movement and reward.
Substantive due process
Substantive due process is a US constitutional law doctrine holding that the Fifth and Fourteenth Amendments' due process clauses protect fundamental rights, such as privacy, marriage, and parenting, from government interference.
Substantive procedures
Substantive procedures are audit procedures designed to detect material misstatements at the assertion level, comprising tests of details and substantive analytical procedures, required regardless of assessed control risk.
Substation
A substation is a node in the electrical grid where voltage is transformed between levels and circuits are switched, connecting generation, transmission, and distribution; the US grid has over 55,000 transmission substations.
Substation automation
Substation automation applies microprocessor-based intelligent electronic devices, communication networks, and software to monitor, control, and protect power substation equipment, replacing electromechanical relays and governed by the IEC 61850 standard.
Substituent
A substituent, or substituent group, is an atom or group of atoms that replaces hydrogen atoms on a parent structure in a molecule, governing both IUPAC nomenclature and chemical reactivity.
Substitute (association football)
Substitute (association football): a named replacement player under IFAB Law 3. Up to five substitutes, three opportunities in top competitions, ten-second exit rule from 2026/27, plus concussion and return-substitute variants.
Substitute good
A substitute good is a product a consumer can use in place of another, like tea and coffee, so a price rise for one raises demand for the other.
Substitute king ritual
The substitute king ritual, called šar pūḫi, was a Neo-Assyrian rite in which a proxy was enthroned and killed to take an omen-predicted death in the king's place.
Substituted amphetamine
Substituted amphetamine, or amphetamine derivative, is a derivative of amphetamine in which hydrogen atoms are replaced by other functional groups, including methamphetamine, MDMA, and ephedrine.
Substitution cipher
A substitution cipher, also called a simple or monoalphabetic substitution cipher, is an encryption method replacing each plaintext letter by another symbol according to a fixed key.
Substitution effect
The substitution effect is the change in demand for a good caused purely by its relative price changing, with utility held constant; it is one half of the Slutsky decomposition.