All articles starting with S
44,216 articles
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.
Substitution therapy
Substitution therapy is medical treatment that supplies a substance the body lacks, such as a hormone, enzyme, or clotting factor, or replaces an addictive drug.
Substitution tiling
A substitution tiling, also called tile substitution, is a tiling generated by rules that enlarge each tile and subdivide it into smaller tiles, producing aperiodic tilings like the Penrose tilings.
Substrait
Substrait is an open, cross-language specification (Protobuf-based, Apache-2.0) for exchanging relational-algebra query plans between data engines, distinct from Apache Arrow (data format) and Calcite (internal IR), with SDKs and IBM-run compliance testing.
Substrate (chemistry)
In chemistry, a substrate is the chemical species whose reaction with another reagent is under observation, for example a compound transformed under the influence of a catalyst.
Substrate ablation
Substrate ablation is a catheter-based strategy for ventricular tachycardia that modifies the scar and border-zone tissue sustaining reentry, developed for VT that is unmappable, noninducible, or hemodynamically intolerable.
Substrate integrated waveguide
A substrate integrated waveguide (SIW) is a planar transmission line that reproduces a rectangular metallic waveguide inside a printed circuit board, developed in the early 2000s.
Substrate reduction therapy
Substrate reduction therapy is an oral treatment for lysosomal storage disorders that partially inhibits synthesis of the accumulating substrate, an alternative to enzyme replacement therapy.
Substrate Specificity
Substrate specificity: the degree to which an enzyme acts on one substrate rather than others, measured by kcat/KM. Related to enzyme promiscuity, substrate ambiguity, patchwork evolution, and directed evolution screening.
Substrate terminology for lichens
Substrate terminology for lichens: substrate/substratum definitions and -colous terms (corticolous, saxicolous, lignicolous, terricolous, muscicolous, lichenicolous), substrate chemistry, specificity, and unusual surfaces like glass and shells.
Substrate-level phosphorylation
Substrate-level phosphorylation (SLP) is direct enzyme-catalyzed transfer of phosphate from a high-energy substrate to ADP, forming ATP without electron transport. Occurs in glycolysis (phosphoglycerate kinase, pyruvate kinase) and the TCA cycle (succinyl-CoA synthetase); oxygen-independent, yielding 2 net ATP per glucose in glycolysis.