Chemistry terminology · MLC-0109

Chemistry terms: S (1,437)

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• Stereospecifically labelled tracerA tracer molecule in which an isotopic label, such as deuterium or carbon-13, is incorporated at a specific...
• StereospecificityA characteristic of a reaction in which stereoisomeric reactants yield stereoisomerically different products...
• Steric effectThe influence on a molecule's properties or reactivity arising from the spatial arrangement and size of its...
• Steric factorA parameter in collision theory that accounts for the orientation of molecules during a collision...
• Steric field-flow fractionationA field-flow fractionation mode for particles larger than about 1 micrometre, in which the cross-field...
• Steric hindranceThe slowing or prevention of a chemical reaction or conformational change due to the spatial bulk of...
• Steric isotope effectA change in the equilibrium constant or rate of a reaction when an atom is replaced by one of its isotopes...
• Steric stabilisationA mechanism by which colloidal particles are prevented from aggregating through the adsorption or grafting of...
• Steric-approach controlA model used to predict the stereochemical outcome of a reaction, particularly additions to carbonyl...
• SterilityThe complete inability of an individual to reproduce, because functional gametes are not produced or...
• SterilizationA process that eliminates or deactivates all forms of microbial life, including bacteria, viruses, fungi, and...
• Stern layerThe inner part of the electrical double layer surrounding a charged surface in an electrolyte solution, where...
• Stern-Volmer kinetic relationshipsEquations that describe the quenching of fluorescence or phosphorescence by a quencher molecule. These...
• SteroidA compound built on the four-ring steroid nucleus, a gonane skeleton in which three six-membered rings are...
• Steroid 21-monooxygenaseAn enzyme, also known as 21-hydroxylase, that catalyzes the hydroxylation of steroids at the C-21 position...
• Steroidogenesis assayA procedure for quantifying the production of steroid hormones from cholesterol precursors. It is used in...
• Steroids, see Steroid
• Sterol lipidsA class of lipids characterized by a core steroid structure, typically with a hydroxyl group at the C-3...
• SterolsA class of steroids that contain a hydroxyl group at the C-3 position of the A-ring and a branched aliphatic...
• Stevens-Johnson syndromeA rare, severe mucocutaneous reaction, most often triggered by drugs such as allopurinol, anticonvulsants...
• Stevenson’s ruleA principle in mass spectrometry stating that the charge in a dissociative ionization process tends to reside...
• StibanesSaturated hydrides of trivalent antimony with the general formula SbnHn+2, of which stibane, SbH3, is the...
• StibanylidenesReactive antimony species of the formula RSb:, in which antimony carries one organic substituent, named as...
• StibinesOrganic compounds containing at least one antimony-carbon bond, formally derived from stibine (SbH3) by the...
• Stibonium compoundsOrganic compounds containing a pentavalent antimony atom, Sb, bonded to four organic groups and carrying a...
• Sticking coefficientThe probability that a gas molecule impinging on a surface will adsorb onto that surface rather than...
• Sticking probabilityThe likelihood that a molecule striking a surface will remain adsorbed to it, rather than desorbing or...
• Sticky endsSingle-stranded nucleotide sequences at the ends of a double-stranded DNA molecule, created when a...
• StillbirthThe death of a fetus in the uterus or during birth after a specific gestational age. This event is...
• StimulantA psychoactive substance that temporarily increases alertness, attention, and energy by enhancing the...
• Stimulated emissionThe process by which an excited atom or molecule, when perturbed by an incident photon of appropriate energy...
• Stimulated radiative charge carrier recombinationRadiative recombination of an electron and a hole that is triggered by an incident photon of matching...
• Stimulated Raman scatteringA non-linear optical process where an intense pump laser beam and a Stokes laser beam interact with a sample...
• Stimuli-responsive polymerA macromolecule that undergoes a reversible or irreversible change in its chemical or physical properties in...
• StimulusAny detectable change in the internal or external environment that can evoke a response in an organism or a...
• Stimulus-responsive polymerA polymer material that exhibits a noticeable and often reversible change in its properties, such as...
• Stir bar sorptive extractionA sample preparation technique that uses a stir bar coated with a sorbent material to extract analytes from a...
• Stirred flow reactorA type of chemical reactor where reactants are continuously fed into a vessel and products are continuously...
• StochasticDescribing a process or phenomenon that involves randomness or probability, where the outcome cannot be...
• Stochastic effectA biological effect whose probability of occurrence is a function of dose, without a threshold, and whose...
• Stochastic samplingA method of selecting a subset of individuals or items from a larger population where each member has a...
• Stochastic theoriesApproaches in chemical kinetics that describe the time evolution of a chemically reacting system as a...
• Stock solutionA concentrated solution of a chemical substance prepared for later dilution to a working concentration. This...
• StoichiometricRelating to the quantitative relationships between reactants and products in a chemical reaction, based on...
• Stoichiometric concentrationThe concentration of a substance in a solution or mixture, expressed in terms of its chemical formula...
• Stoichiometric mean molalA measure of the average molality of ions in an electrolyte solution, taking into account the stoichiometric...
• Stoichiometric numberThe coefficient of a species in a balanced stoichiometric equation, written with a negative sign for each...
• Stoichiometric sputteringThe process where the composition of the sputtered material from a target surface is identical to the bulk...
• StoichiometryThe quantitative relationship between reactants and products in a chemical reaction, based on the law of...
• StokesA non-SI unit of kinematic viscosity, defined as one square centimeter per second (1 St = 1 cm^2/s). It is...
• Stokes equationAn equation that describes the drag force experienced by a spherical particle moving through a viscous fluid...
• Stokes lawA physical law describing the drag force on a spherical particle moving through a viscous fluid at low...
• Stokes numberA dimensionless quantity representing the ratio of the stopping distance of a particle to a characteristic...
• Stokes parametersA set of four values that completely describe the polarization state of electromagnetic radiation, including...
• Stokes shiftThe difference in wavelength or frequency between the maximum of the absorption spectrum and the maximum of...
• Stokes type radiationElectromagnetic radiation emitted by a substance at a longer wavelength (lower energy) than the exciting...
• Stokes-Einstein equationA relationship that describes the diffusion coefficient of a spherical particle in a liquid, relating it to...
• Stokes-Raman scatteringThe inelastic scattering of photons by molecules, where the scattered photons have lower energy (longer...
• Stop eventThe detection of an ion arrival at the detector in time-of-flight secondary-ion mass spectrometry, registered...
• Stop-flow conditionsOperating conditions in electrothermal atomic absorption spectrometry in which the flow of inert purge gas...
• Stopped flowA rapid mixing technique used to study the kinetics of fast chemical reactions, particularly those occurring...
• Stopped-flow cellA device for studying the kinetics of fast chemical reactions in solution by rapidly mixing two or more...
• StopperA bulky group covalently attached to the ends of a linear component, preventing its dethreading from a...
• Stopping cross sectionA measure of the energy loss per unit path length experienced by an energetic particle traversing a material...
• Stopping cross section factorA quantity used in ion scattering and Rutherford backscattering analysis that links the energy lost by a...
• Stopping powerThe mean energy lost per unit path length by a charged particle moving through a material, S = -dE/dx. Energy...
• Storage modulusA measure of the elastic response of a material under oscillatory deformation, representing the energy stored...
• Stored waveform inverse fourier transformA method used in Fourier transform ion cyclotron resonance mass spectrometry to excite ions to detectable...
• STPStandard temperature and pressure, the reference conditions for reporting gas volumes, which IUPAC sets at...
• StrainThe destabilization of a molecule due to deviations from ideal bond lengths, bond angles, or non-bonded...
• Strain energyThe excess potential energy stored within a molecule due to its deviation from an idealized, strain-free...
• Strain-induced transitionA phase transition in a solid material that is directly caused by the application of mechanical strain. The...
• Strand breakA disruption in the phosphodiester backbone of a nucleic acid molecule, such as DNA or RNA. This can occur as...
• StratificationThe formation or arrangement of a material or medium in distinct layers, such as sediment laid down in beds...
• Stratified filmA thin liquid film, such as a soap or foam film, in which several distinct thicknesses coexist side by side...
• Stratified sampleA sample obtained by dividing the population into several subpopulations, or strata, and then taking a random...
• Stratified samplingA sampling procedure in which a heterogeneous population is first divided into distinct, non-overlapping...
• Stratocumulus cloudA low-level cloud formation characterized by large, rounded masses or rolls that are grouped together in a...
• StratopauseThe boundary layer in the Earth's atmosphere between the stratosphere and the mesosphere, marking the level...
• StratosphereThe layer of Earth's atmosphere situated above the troposphere and extending upwards to the stratopause. This...
• Stratus cloudA type of low-level cloud characterized by horizontal layering with a uniform, gray base. These clouds form...
• Stray lightAny light reaching the detector in a spectroscopic instrument that is outside the nominal wavelength or...
• Stray radiation errorAn error in spectrophotometric measurements caused by the presence of stray light reaching the detector. This...
• Streak tubeA type of image converter tube that converts an optical image into an electron image, which is then swept...
• StreamThe sample solution in a membrane separation before it contacts the membrane, which is the feed side from...
• Streaming birefringenceThe phenomenon where an optically isotropic fluid becomes birefringent when subjected to a shear flow. This...
• Streaming currentAn electric current generated when an electrolyte solution flows through a capillary or porous plug, causing...
• Streaming potential differenceAn electric potential difference that develops across a porous medium or capillary when an electrolyte...
• StressThe physiological or psychological response of an organism to a physical, chemical, or emotional factor...
• Stress graphitizationThe process of converting non-graphitic carbon materials into graphitic structures under the combined...
• Stress proteinsA group of proteins synthesized by cells in response to environmental stressors, such as heat, cold, or...
• Stress relaxationThe time-dependent decrease in stress within a material when it is subjected to a constant strain. This...
• Stress theory of agingA hypothesis that stress shortens lifespan by accelerating energy expenditure, so organisms exposed to more...
• Stress-assisted transitionA phase transformation in a solid material that is influenced or promoted by the application of mechanical...
• StressorAn agent, condition, or stimulus that causes stress in an organism or ecosystem, leading to a physiological...
• Stress-protein fingerprintingA technique used to identify and quantify the specific pattern of stress protein expression in an organism or...
• Stress-response pathwayA series of interconnected molecular events within a cell or organism that are activated in response to a...
• StriatumA major subcortical structure of the forebrain, forming a key part of the basal ganglia. It is composed...
• StrippingThe transfer of a solute from an organic phase, where it has been concentrated by extraction, back into an...
• Stripping phaseThe phase used to remove a solute from another phase in a separation process, particularly in liquid-liquid...
• Stripping reactionA reaction in which a projectile pulls an atom or group off a target in a distant, glancing collision, so the...
• Stripping solutionAn aqueous solution used to transfer a solute from an organic solvent back into an aqueous phase during a...
• Stripping voltammetryAn electrochemical analytical technique that involves two main steps: an initial preconcentration step where...
• StrokeA medical condition resulting from an interruption of blood supply to a part of the brain, leading to brain...
• Stromal cellA cell that forms the connective tissue of an organ, providing structural support and secreting extracellular...
• Strong collisionA collision between molecules that results in a complete redistribution of energy among the internal degrees...
• Strong glassA type of glass-forming liquid characterized by a relatively small change in viscosity with temperature near...
• Structural alertA specific chemical substructure or functional group within a molecule that is known or predicted to be...
• Structural disorderAny deviation from a perfectly ordered, periodic arrangement of atoms or molecules within a material. This...
• Structural diversityThe variety of physical forms, arrangements, or architectures within a biological community or ecosystem...
• Structural formulaA chemical formula that shows the arrangement of atoms in a molecule, indicating how atoms are bonded to each...
• Structural keysA type of molecular fingerprint representing the presence or absence of predefined chemical substructures or...
• Structural lipidsA class of lipids that are major components of biological membranes, providing the structural framework for...
• Structural proteomicsA subfield of proteomics focused on determining the three-dimensional structures of proteins, their...
• Structural stabilityA property of a molecular structure sitting at an energy minimum on the potential energy surface within the...
• Structural transitionA phase transition in a solid material that involves a change in its crystal structure. This transformation...
• StructureThe spatial arrangement of atoms or ions within a solid catalyst, particularly at its surface. This...
• Structure diagramA two-dimensional graphical representation of the internal structure of a chemical species that depicts the...
• Structure-activity relationshipThe correlation between the chemical structure of a substance and its biological or toxicological activity...
• Structure-based designA drug discovery approach that relies on the three-dimensional structure of a biological target, such as a...
• Structure-data format fileA chemical file format that contains information for one or more molecules, including 2D or 3D atomic...
• Structure-metabolism relationshipAn association between the chemical structure of a substance and its metabolic fate within an organism...
• Structure-property correlationsRelationships that describe how the chemical structure of a substance influences its physical, chemical, or...
• StuporA state of severely reduced mental and physical activity, characterized by unresponsiveness to external...
• Sturm testA standardized laboratory test used to assess the ultimate biodegradability of organic chemicals in an...
• StygobiontAn aquatic animal that is obligately adapted to living its entire life in subterranean groundwater habitats...
• StygophileAn aquatic animal that lives in and is capable of completing its life cycle within both subterranean...
• StyphnatesCompounds formed from styphnic acid, a strongly acidic trinitro derivative of resorcinol, as either salts or...
• Styrene polymerA polymer derived from the monomer styrene, characterized by a repeating unit containing a phenyl group...
• Subacute cutaneous lupus erythematosusA distinct form of cutaneous lupus erythematosus characterized by non-scarring, photosensitive skin lesions...
• SubarachnoidRelating to the space located between the arachnoid mater and the pia mater, two of the three meningeal...
• Subarachnoid hemorrhageAn extravasation of blood into the subarachnoid space, which is the fluid-filled area located between the...
• SubchainA segment of a polymer chain that is defined by specific points along its length, often between cross-links...
• SubchronicRelating to a period of exposure or a study of intermediate duration, which is longer than an acute exposure...
• Subchronic effectAn adverse biological effect resulting from repeated or continuous exposure to a chemical for a duration that...
• Subchronic toxicity testA study designed to evaluate the adverse effects of a substance when administered repeatedly to experimental...
• Subclinical effectA biological change or disease state that is not yet severe enough to produce overt clinical signs or...
• SubcooledA liquid whose temperature is below the saturation temperature for its existing pressure, so it is not yet at...
• Subcooled liquid vapour pressureThe vapor pressure of the liquid form of a substance at a temperature below its melting point, where the...
• SubduralRelating to the space located beneath the dura mater, which is the outermost and toughest of the three...
• SubfertilityA state of reduced fertility, indicating a longer than average time to conceive or a lower probability of...
• Subgroup-supergroup transitionA type of structural phase transition where the symmetry of the lower-temperature phase (subgroup) is a...
• Subjacent orbitalA molecular orbital next to the frontier orbitals, namely the next-to-highest occupied orbital (NHOMO) just...
• Subjective environmentThe environment as it is perceived and experienced by an individual, encompassing personal feelings, social...
• SublationA separation technique where a solute is adsorbed onto the surface of gas bubbles rising through a liquid...
• SublibraryA smaller, more focused collection of compounds or molecules derived from a larger chemical library, often...
• SublimationThe direct transition of a substance from the solid state to the vapour state without passing through a...
• Sublingual tabletsSolid dosage forms designed to dissolve rapidly when placed under the tongue, allowing for direct absorption...
• SubsampleA portion of a sample taken for analysis or for storage, which is assumed to be representative of the...
• Sub-shell photoionization cross sectionA measure of the probability that a photon of a given energy will eject an electron from a specific atomic...
• Subsidiary lamellaeThin, plate-like crystalline structures that form within a polymer, growing from the surfaces of dominant...
• Substance contentA quantity from clinical chemistry nomenclature, obtained by dividing the moles of a component present by the...
• Substance flow rateThe rate at which a specific chemical substance is transported through a system or across a boundary per unit...
• Substance fractionThe ratio of the amount of a specific substance to the total amount of all substances in a mixture. This...
• Substantia nigraA nucleus in the midbrain, part of the basal ganglia, that has a major role in motor control, reward, and...
• Substituent atomAn atom that replaces a hydrogen atom or another atom in a parent molecule, forming a derivative. This atom...
• Substitution chain transferA chain transfer reaction in polymerization where a radical abstracts an atom or group from a molecule...
• Substitution reactionA chemical reaction in which one atom or group of atoms in a molecule is replaced by another atom or group of...
• Substitutive nameA systematic name for a chemical compound derived by identifying a parent hydride or parent compound and then...
• Substoichiometric extractionA solvent extraction technique where the amount of extractant added is less than the stoichiometric quantity...
• Substoichiometric isotope dilution analysisA radiochemical method for determining the concentration of a substance by adding a known amount of its...
• SubstrateA chemical species that undergoes a transformation during a reaction, often catalyzed by an enzyme or another...
• Substructure searchingA computational method used to identify molecules that contain a specific chemical fragment or pattern within...
• SubthalamusA small region of the diencephalon, located ventral to the thalamus and medial to the internal capsule. It...
• Subtractive nameA name built from a parent structure plus an affix showing that atoms or groups have been taken away, with...
• SubunitA building block of a constitutional repeating unit: the biggest piece of its backbone that organic...
• SuccessionThe progressive and somewhat predictable process of change in the species composition of an ecological...
• Successor complexAn encounter complex that has undergone a chemical transformation, such as electron transfer, but where the...
• Sudden polarizationStrong charge separation inside a polyene or related molecule that appears in its excited singlet state after...
• Sufficient evidenceA body of data and information that establishes a causal relationship between an exposure and an adverse...
• SugarA carbohydrate, specifically a saccharide, characterized by a sweet taste and typically containing carbon...
• Sugars, see Sugar
• Suggested no-adverse-response levelA proposed concentration or dose of a substance below which no adverse health effects are expected to occur...
• Suicide reactionA reaction in which a DNA-processing enzyme, typically a topoisomerase, becomes covalently and irreversibly...
• SulcusA groove or furrow on the surface of an organ, particularly the brain. These indentations increase the...
• Sulfamic acidsAmides of sulfuric acid of the type R-NH-SO2-OH, among them the parent H2N-SO2-OH. In water the parent...
• SulfanesCompounds consisting of chains of sulfur atoms terminated by hydrogen atoms, with the general formula H2Sn...
• SulfatidesA class of sulfated glycosphingolipids, which are lipids containing a carbohydrate group and a sulfate ester...
• SulfenamidesOrganic compounds characterized by the presence of a sulfur-nitrogen single bond, with the general formula...
• SulfenesHighly reactive transient species of the formula R2C=SO2, formally the S,S-dioxide of a thioaldehyde or...
• Sulfenic acidsOrganosulfur compounds of the formula RSOH, with a hydroxyl group on divalent sulfur, the lowest oxidation...
• Sulfenium ionsAn incorrect name sometimes applied to sulfenylium ions, the cations of formula RS+ in which a single organic...
• Sulfenyl groupsMonovalent functional groups with the general structure -SR, where R represents an organic substituent. These...
• Sulfenyl radicalsReactive intermediates with the general structure RS•, where the unpaired electron is formally localized on...
• Sulfenylium ionsCations of the formula RS+, with a single organic group on a positively charged sulfur atom; the synonymous...
• SulfidesOrganic compounds containing a sulfur atom bonded to two organic groups, with the general formula R-S-R'...
• SulfimidesCompounds characterized by a sulfur-nitrogen double bond, typically with the general structure R2S=NR', where...
• SulfinamidesOrganic compounds containing a sulfinyl group (-S(O)-) bonded to an amino group, with the general formula...
• SulfinamidinesDerivatives of sulfinic acids in which both oxygen atoms are replaced by nitrogen, giving the structure...
• Sulfinic acidsOrganic compounds containing the -S(O)OH functional group, where sulfur is directly bonded to an organic...
• Sulfinic anhydridesA class of organic compounds characterized by the general formula R-S(O)-O-S(O)-R', where R and R' represent...
• SulfinylaminesOrganic compounds containing the sulfinylamino functional group, -N=S=O, attached to an organic moiety. These...
• SulfolipidsA class of lipids containing a sulfur-linked functional group, such as a sulfonate group, or a lipid that is...
• SulfonamidesOrganic compounds containing a sulfonyl group, -SO2-, directly attached to a nitrogen atom, forming the...
• SulfonamidinesOrganic compounds that are derivatives of sulfonamides, where one of the oxygen atoms of the sulfonyl group...
• SulfonediiminesCompounds of the type R2S(=NR')2, formally derived from sulfones by replacing both oxygen atoms with imino...
• SulfonesA class of organic compounds containing a sulfonyl functional group, -SO2-, where the sulfur atom is directly...
• Sulfonic acidsOrganic compounds containing the sulfo functional group, -SO3H, where a sulfur atom is directly bonded to a...
• Sulfonic anhydridesCompounds of the structure RSO2-O-SO2R', formally made from two sulfonic acid molecules by loss of one water...
• Sulfonium compoundsOrganic compounds containing a trivalent sulfur atom bonded to three hydrocarbyl groups, forming a positively...
• SulfonphthaleinsA class of organic compounds characterized by a central carbon atom bonded to two phenol rings and a sulfonyl...
• SulfonylaminesCompounds of the structure RN=SO2, in which nitrogen carries one organic group and is doubly bonded to a...
• SulfoxidesOrganic compounds containing a sulfinyl functional group (R-S(O)-R'), where the sulfur atom is double-bonded...
• SulfoximidesOrganic compounds containing a sulfoximine functional group, characterized by a sulfur atom double-bonded to...
• Sulfur diimidesOrganic compounds containing a sulfur atom double-bonded to two nitrogen atoms, each of which is bonded to a...
• SultamsCyclic sulfonamides, which are heterocyclic compounds containing a sulfur atom and a nitrogen atom within a...
• SultimsTautomeric forms of sultams in which the hydrogen of the ring NH has shifted to a sulfonyl oxygen, leaving a...
• SultinesA class of heterocyclic organosulfur compounds that are cyclic esters of a sulfinic acid. They are analogous...
• SultonesCyclic esters of hydroxy sulfonic acids, in which a sulfonyl group (SO2) in the ring is bonded to a ring...
• Sum bandAn absorption or emission band in a vibrational spectrum that arises from the simultaneous excitation of two...
• Sum frequency generation spectroscopyA non-linear optical spectroscopic technique that probes surfaces and interfaces by generating a signal at...
• Sum of statesThe total number of accessible quantum states of a system, such as a molecule or a collection of molecules...
• Sum transitionA spectroscopic transition that occurs when a molecule simultaneously absorbs energy corresponding to the sum...
• Sum-frequency spectroscopyA nonlinear optical spectroscopic method that involves the interaction of two incident laser beams with...
• Summary sheetA short document, typically two to four pages, that condenses a risk assessment into its principal findings...
• SummationThe adding together of separate postsynaptic potentials produced by inputs that arrive close together in time...
• Summit currentThe maximum current observed in a polarographic or voltammetric curve, particularly in techniques like...
• Summit potentialThe potential at which the maximum current is observed in a polarographic or voltammetric experiment...
• Superabsorbent polymerA polymeric material capable of absorbing and retaining extremely large quantities of liquid relative to its...
• SuperacidAn acidic medium with a proton-donating ability greater than that of pure sulfuric acid. Its acidity is...
• SuperantigenA class of antigens that activate a large fraction of T lymphocytes by binding simultaneously to the T-cell...
• Superconducting transitionA phase transition occurring in certain materials when cooled below a critical temperature, at which point...
• SupercooledDescribing a liquid that has been cooled below its normal freezing point without solidifying. This metastable...
• Supercooled meltA liquid substance that has been cooled below its equilibrium freezing or melting point without solidifying...
• Supercooled polymer meltA polymer melt that has been cooled below its equilibrium melting temperature but remains in a liquid...
• SupercoolingThe metastable condition of a liquid, in polymers a melt, cooled below its equilibrium melting temperature...
• Supercritical drying of a gelA drying technique that removes solvent from a gel by passing through the critical point of the solvent...
• Supercritical fluidA substance existing at a temperature and pressure exceeding its critical point, the specific threshold where...
• Supercritical fluid chromatographyA chromatographic technique that uses a supercritical fluid as the mobile phase to separate components of a...
• Supercritical fluid chromatography-mass spectrometryA hyphenated analytical technique that couples supercritical fluid chromatography (SFC) for separation with...
• Supercritical fluid extractionAn extraction process that uses a supercritical fluid as the extraction solvent to separate one component...
• Superequivalent adsorptionThe adsorption of counter-ions onto a charged surface in an amount exceeding the initial surface charge...
• Superexchange interactionA long-range magnetic coupling between two non-adjacent paramagnetic centers that is mediated through a...
• SuperfamilyA large grouping of proteins or genes believed to have diverged from a distant common ancestor. Members of a...
• SuperfecundationA situation in which two or more ova shed during a single ovulatory period are fertilized by sperm from...
• SuperfetationThe rare occurrence of a second conception during an ongoing pregnancy, resulting in the presence of two...
• Superficial workThe work done per unit area to create or expand a surface, representing the energy required to bring...
• SuperfundA United States federal government program designed to fund the cleanup of sites contaminated with hazardous...
• Superjacent orbitalThe molecular orbital lying immediately above the lowest unoccupied molecular orbital in energy, that is, the...
• SuperlatticeA periodic arrangement of atoms or molecules in a material that has a larger periodicity than the underlying...
• SupernumeraryDescribing an anatomical structure, such as an organ, tooth, or digit, that is present in excess of the...
• Superoxide dismutaseAn enzyme that converts two superoxide radicals into one molecule of oxygen and one of hydrogen peroxide, a...
• SuperposabilityThe property of two or more three-dimensional objects, such as molecules or their models, that allows them to...
• SuperradianceThe cooperative spontaneous emission of radiation by an ensemble of excited atoms or molecules, resulting in...
• Supersaturated solutionA solution that contains a greater amount of dissolved solute than would normally be present at equilibrium...
• SupersaturationA condition in which a solution contains a greater amount of dissolved solute than it would normally hold at...
• Supervised classificationA chemometric method for categorizing unknown samples into predefined classes based on a training set of...
• Supervised learningA type of machine learning where an algorithm learns from a labeled dataset, meaning each input data point is...
• SupportAn inert material, typically porous and with a high surface area, onto which an active catalytic component is...
• Support plateA rigid, inert sheet, typically made of glass, aluminum, or plastic, onto which a thin layer of adsorbent...
• Support-coated open-tubular columnA type of capillary column used in gas chromatography where the inner wall of the tube is coated with a...
• Supported liquid membraneA separation device consisting of a porous polymeric membrane whose pores are filled with an immiscible...
• Supporting electrolyteAn electrolyte added in high concentration to a solution containing an electroactive substance to conduct the...
• SuppositoriesSolid dosage forms designed for insertion into body cavities other than the mouth, such as the rectum...
• SuppressionA reduction in the magnitude or activity of a biological response, particularly within the immune system...
• SuppressorA component in an analytical system that reduces or eliminates an unwanted signal or interference. In...
• Suppressor cellA lymphocyte that downregulates the immune response by inhibiting the activity of other immune cells, such as...
• Supramolecular adhesion complexAn organized cluster of proteins and lipids at the interface between two cells that mediates cell-to-cell...
• Supramolecular assemblyA structured aggregate of two or more molecules held together by non-covalent interactions, such as hydrogen...
• Supramolecular associationThe formation of a complex entity from two or more chemical species held together by non-covalent...
• Supramolecular chemistryA field of chemistry concerned with chemical systems composed of a discrete number of interacting molecular...
• SupramoleculeA well-defined chemical entity formed by the non-covalent association of two or more molecular entities...
• SupratentorialDescribing anatomical structures or pathological processes located above the tentorium cerebelli, a dural...
• Supratentorial herniationThe displacement of brain tissue from the supratentorial compartment into an adjacent compartment, typically...
• SurfaceThe outermost layer of a material, which forms the boundary between two phases, such as a solid and a gas or...
• Surface amountThe excess amount of a substance accumulated at an interface between two bulk phases, compared to the amount...
• Surface barrier semiconductor detectorA type of semiconductor radiation detector fabricated by creating a rectifying junction at the surface of a...
• Surface charge densityThe quantity of electric charge present per unit area of a surface, denoted by the Greek letter sigma (σ). It...
• Surface chemical potentialThe change in the Gibbs energy of a system when an infinitesimal amount of a substance is added to the...
• Surface concentrationThe amount of a substance present per unit area at an interface, such as the boundary between a solid and a...
• Surface contaminationAny foreign material, either as a continuous layer or as discrete particles, that is unintentionally present...
• Surface core-level shiftA change in the binding energy of core electrons for atoms located at the surface of a material compared to...
• Surface coverageA measure of the fraction of available surface sites occupied by adsorbed species on a solid surface. It is...
• Surface crossingA transition between two electronic potential energy surfaces of a molecule, occurring when the molecule's...
• Surface densityA quantity per unit area, representing the concentration of a physical quantity on a two-dimensional surface...
• Surface dipole layerA region at an interface where there is a net orientation of molecular dipoles, creating an electric...
• Surface electric potentialThe potential drop across the dipole layer at the surface of a phase, equal to the inner electric potential...
• Surface excessA measure of the concentration of a component at an interface, relative to its concentration in the bulk...
• Surface excess amountThe excess of the amount of a component actually present in an interfacial system over the amount in a...
• Surface excess concentrationThe amount of a specific component present at an interface, beyond what would be expected if the bulk...
• Surface excess conductivityThe additional electrical conductivity observed at an interface or surface compared to the bulk phase. It...
• Surface excess energyThe additional energy associated with the molecules at an interface, compared to the energy they would...
• Surface excess enthalpyThe enthalpy associated with the formation of an interface, representing the difference in enthalpy between...
• Surface excess entropyThe entropy associated with the molecules located at an interface, relative to the entropy they would have in...
• Surface excess Gibbs energyThe excess Gibbs energy associated with the formation of an interface between two phases, relative to the...
• Surface excess Helmholtz energyThe Helmholtz energy associated with the formation of an interface, representing the work required to create...
• Surface excess isothermA graph that illustrates the relationship between the surface excess concentration of a component and its...
• Surface extended X-ray absorption fine structure spectroscopyA form of extended X-ray absorption fine structure measurement in which the absorption is tracked through the...
• Surface graftingA process where polymer chains are covalently attached to the surface of a substrate, forming a brush-like...
• Surface ionizationAn ionization process where atoms or molecules are adsorbed onto a heated surface and subsequently desorb as...
• Surface ionsIons located at the interface between a solid material and its surrounding medium, such as a liquid or gas...
• Surface layerThe region of a phase that is immediately adjacent to an interface and exhibits properties different from the...
• Surface mapA two-dimensional representation showing the spatial distribution of a specific chemical element, compound...
• Surface of a phaseA mathematical surface that separates two homogeneous phases, representing the region where the properties of...
• Surface of tensionA dividing surface placed inside the interfacial layer between two fluids so that the layer is treated...
• Surface plasmonA collective oscillation of free electrons at the interface between a metal and a dielectric material. These...
• Surface plasmon resonanceA phenomenon involving the resonant excitation of surface plasmons by incident light, typically at a...
• Surface plasmon resonance assayAn optical technique used to detect and quantify molecular interactions in real time without the need for...
• Surface pressureThe reduction in surface tension of a liquid caused by the presence of a monolayer of adsorbed molecules at...
• Surface recombinationThe process where photogenerated electron-hole pairs in a semiconductor material recombine at the surface or...
• Surface regionThe portion of a material that encompasses the interface and extends into the bulk phase, where properties...
• Surface righting testA behavioral test used in neurotoxicology to assess an animal's ability to correct its posture when placed on...
• Surface roughnessA measure of the texture of a polymer surface, quantifying the deviations in the direction of the surface...
• Surface segregationThe phenomenon where certain components of a multi-component material preferentially accumulate at the...
• Surface shear viscosityA measure of the resistance of a fluid interface to tangential deformation or flow. It quantifies the energy...
• Surface statesElectronic energy levels that exist at the surface of a material, distinct from the bulk energy bands. These...
• Surface stressThe force per unit length acting within a surface, representing the reversible work required to elastically...
• Surface tensionThe force per unit length acting parallel to the surface of a liquid, tending to minimize the surface area...
• Surface workThe work required to increase the surface area of a phase by a differential amount, against the forces of...
• Surface-active siteA specific location on the surface of a solid material, such as a catalyst or adsorbent, where chemical...
• Surface-assisted laser desorption/ionization mass spectrometryA variant of matrix-assisted laser desorption/ionization in which the matrix is a combination of a liquid and...
• Surface-average particle diameterA statistical measure of particle size in a dispersed system, calculated as the diameter of a sphere having...
• Surface-bound macrocyclic sorbentA type of sorbent material where macrocyclic compounds are chemically immobilized onto a solid support...
• Surface-bound phenylboronic acid sorbentA material used in extraction processes where phenylboronic acid groups are chemically attached to a solid...
• Surface-enhanced hyper-Raman spectroscopyA spectroscopic technique that combines the principles of hyper-Raman scattering with surface enhancement...
• Surface-enhanced infrared absorptionAn analytical technique that amplifies the infrared absorption signals of molecules adsorbed onto a metallic...
• Surface-enhanced infrared spectroscopyA spectroscopic method that significantly amplifies the infrared absorption or reflection signals of...
• Surface-enhanced laser desorption/ionizationAn adaptation of matrix-assisted laser desorption/ionization in which the sample target is coated with...
• Surface-enhanced Raman spectroscopyA spectroscopic technique that significantly amplifies the Raman scattering signal from molecules adsorbed...
• Surface-enhanced resonance Raman spectroscopyA spectroscopic technique that combines the signal amplification of surface-enhanced Raman spectroscopy with...
• Surface-enhanced resonant Raman spectroscopyA spectroscopic technique that combines the principles of surface-enhanced Raman spectroscopy (SERS) with...
• Surface-enhanced, spatially offset Raman spectroscopyA variant of Raman spectroscopy that combines the signal enhancement from a nanostructured metallic surface...
• Surface-induced dissociationA tandem mass spectrometry technique where ions are fragmented by colliding them with a solid surface at low...
• Surface-induced reactionA chemical reaction that occurs when an ion or molecule collides with a solid surface, resulting in the...
• SurfactantA substance that, when added to a liquid, reduces its surface tension or interfacial tension with another...
• SurfmerA monomer molecule that possesses surface-active properties, meaning it can reduce the surface tension of a...
• SurprisalA quantitative measure of the deviation of an observed probability distribution from a prior, usually...
• Surprisal analysisAn information-theoretic method for analyzing the distribution of product states in a chemical reaction, such...
• SurrogateA substitute or proxy that stands in for another entity or measurement. In toxicology, a surrogate endpoint...
• Surrogate internal standardA compound added to a sample before analysis that is chemically similar to the analyte but not naturally...
• Surrogate light chainA protein complex in developing B lymphocytes that substitutes for a conventional immunoglobulin light chain...
• Surrogate organismA species used in ecotoxicological studies as a substitute for a target species that is difficult to test...
• Surrogate toxicantA chemical substance used in toxicological studies or risk assessments as a representative for a group of...
• SurveillanceThe systematic and ongoing collection, analysis, interpretation, and dissemination of data regarding the...
• Survival timeThe duration from a specific point in time, such as exposure to a toxicant or diagnosis of a disease, until...
• SurvivorshipThe proportion of individuals in a population that remain alive after a specified period or under particular...
• Survivorship curveA graphical representation of the number of individuals in a population that can be expected to survive to...
• SusceptibilityThe inherent sensitivity of an organism or population to the adverse effects of a chemical or environmental...
• SusceptibleDescribing an individual or organism that is likely to be adversely affected by exposure to a toxic agent or...
• Suspended matterSolid particles dispersed within a fluid, such as air or water, that are large enough to be retained on a...
• SuspensionA dispersion of solid particles in a liquid. Particles larger than about a micrometre settle under gravity...
• Suspension effectA phenomenon observed in potentiometric measurements of suspensions, where the measured potential differs...
• Suspension feederAn aquatic organism that obtains food particles by filtering them from the water column. These organisms...
• Suspension of solid charged particlesA heterogeneous system consisting of finely divided solid particles dispersed in a liquid phase, where the...
• Suspension pHA pH meter reading taken in a soil suspension, mixed with water or an electrolyte, by potentiometry carried...
• Suspension polymerisationA heterogeneous polymerization process where monomer droplets are dispersed in an immiscible continuous...
• Suspension potentiometric cellAn electrochemical cell designed for potentiometric measurements, such as pH, in a multiphase system...
• SustainabilityThe principle of satisfying present needs in a way that leaves later generations able to satisfy theirs. In...
• Sustained deliveryThe controlled release of an active substance, such as a drug, from a polymeric matrix over an extended...
• Sustained off-resonance irradiationA technique used in mass spectrometry, particularly in ion traps, to excite ions for collision-induced...
• Sustained releaseA pharmaceutical dosage form designed to release a drug over an extended period, maintaining relatively...
• Swain-Lupton equationA linear free-energy relationship used in physical organic chemistry to quantify the electronic effects of...
• Swain-Scott equationA linear free-energy relationship that correlates the rates of nucleophilic substitution reactions with the...
• SweatA hypotonic aqueous solution secreted by sweat glands, primarily composed of water, electrolytes, and...
• SwellingThe increase in volume of a material, typically a polymer or gel, due to the absorption of a solvent. This...
• Swelling agentA substance that penetrates and expands the volume of a polymeric material, typically a crosslinked network...
• Swelling pressureThe pressure difference that must be applied between a swollen gel and the liquid it is in equilibrium with...
• Swift ionAn ion moving faster than the Bohr speed, c/137, where c is the speed of light and the Bohr speed is that of...
• Swimming testA behavioral assay used in neurotoxicology and psychopharmacology, typically with rodents, to assess motor...
• Swing curveA plot of a lithographic response, such as the dose needed to clear the resist or the printed linewidth...
• Switch sequenceA specific DNA sequence found in the immunoglobulin heavy chain locus that mediates class switching, allowing...
• Switchboard modelA model of polymer crystallinity in which all the crystallized stems of a chain belong to the same crystal...
• Switching transitionA voltage-driven transition in semiconducting glasses, typically chalcogenides, in which an applied field...
• Sydnone iminesMesoionic compounds structurally related to sydnones, where the exocyclic oxygen atom of the sydnone ring is...
• SydnonesA class of five-membered heterocyclic mesoionic compounds, characterized by a 1,2,3-oxadiazole ring with a...
• Sym-A prefix used in chemical nomenclature, particularly for substituted benzene derivatives, to indicate a...
• SymbiosisThe tendency for a central atom or ion to preferentially coordinate with ligands that are either all hard or...
• SymbolA conventional representation of a quantity, unit, or chemical element, typically consisting of one or more...
• SymmetricDescribing a molecule or system that possesses one or more symmetry elements, such as planes of symmetry...
• Symmetric topA type of rigid rotor molecule in which two of the three principal moments of inertia are equal, while the...
• Symmetrical filmsA thin fluid film whose two bounding phases are the same, so the film phase is flanked by identical media on...
• Symmetrical flow field-flow fractionationA separation technique within the field-flow fractionation family where the channel geometry and flow...
• SymmetrizationA data processing procedure applied to two-dimensional nuclear magnetic resonance (2D NMR) spectra to improve...
• Symmetry breakingThe loss, in one crystal polymorph of a polymer, of symmetry elements that appear in other polymorphs or in...
• Symmetry coordinateA linear combination of internal coordinates (bond stretches, angle bends) that transforms according to an...
• Symmetry numberThe number of indistinguishable orientations that a molecule can achieve through simple rotation of the...
• Symmetry-conserving transitionA phase transition where the crystal symmetry of the material remains unchanged between the two phases...
• Symmorphic space groupA space group that contains no screw axes and no glide planes, so that its operations are built from a...
• Sympathetic nervous systemThe part of the autonomic nervous system that mobilizes the body for emergencies, the so-called...
• Sympathetic ophthalmiaA rare, bilateral, diffuse granulomatous inflammation of the uveal tract of both eyes, occurring after...
• SympatholyticDescribing a substance or drug that inhibits the activity of the sympathetic nervous system. These agents...
• SympathomimeticA substance that mimics the effects of stimulating the sympathetic nervous system, often by activating...
• SymptomAny subjective evidence of disease or a change in physical or mental condition as perceived and reported by...
• SymptomatologyThe study or description of symptoms, encompassing their nature, causes, and the patterns in which they...
• SynA stereochemical descriptor for the relative configuration of two substituents on adjacent atoms in an...
• SynapseA specialized junction between two nerve cells, or between a nerve cell and an effector cell, that allows for...
• SynapsisThe pairing of homologous chromosomes during prophase I of meiosis, forming a bivalent structure. This...
• Synaptic cleftThe narrow extracellular space separating the presynaptic neuron from the postsynaptic neuron at a chemical...
• Synaptic inhibitionThe suppression of synaptic transmission, which occurs postsynaptically when an inhibitory transmitter such...
• Synaptic plasticityThe ability of synapses, the junctions between neurons, to modify their strength and efficacy over time. This...
• Synaptic strippingThe process where microglial cells remove synaptic terminals from neurons, leading to a reduction in synaptic...
• Synaptic transmissionThe process by which a neuron communicates with a target cell, such as another neuron or a muscle cell...
• Synaptonemal complexA proteinaceous structure that forms between homologous chromosomes during the pachytene stage of prophase I...
• SyncephalusA form of conjoined twinning in which two bodies are united at the head and upper trunk, so the twins share a...
• SynchronizationThe condition in a chemical reaction where changes in bond lengths and angles occur simultaneously or in a...
• SynchronousA concerted process whose bond formation and bond rupture are equally advanced when the transition state is...
• Synchronously excited spectrumA type of fluorescence spectrum where both the excitation and emission monochromators are scanned...
• Synchrotron radiationElectromagnetic radiation emitted by charged particles, typically electrons, when they are accelerated to...
• Synchrotron radiation induced X-ray fluorescence analysisAn analytical technique that uses highly intense and tunable X-rays from a synchrotron source to excite...
• Synchrotron X-ray spectroscopyA group of analytical techniques that use the high-flux, tunable, and polarized X-ray radiation produced by a...
• SyncytiotrophoblastA continuous, multinucleated layer of epithelial cells covering the surface of the placental villi that forms...
• SyncytiumA multinucleated cell that results from the fusion of multiple individual cells or from multiple nuclear...
• SyndactylyA congenital anomaly characterized by the fusion of two or more digits, either fingers or toes. This...
• SyndetA synthetic detergent, which is a cleaning agent formulated from synthetic chemical compounds rather than...
• Syndiotactic macromoleculeA macromolecule in which the configurational repeating units have alternating relative configurations along...
• Syndiotactic polymerA polymer composed of syndiotactic macromolecules, meaning the substituent groups on successive monomer units...
• SyndromeA collection of signs and symptoms that occur together and characterize a particular disease or abnormal...
• SyneresisThe spontaneous expulsion of liquid from a gel, resulting in the shrinkage of the gel volume. This process...
• SynergismA phenomenon where the combined effect of two or more substances or agents is greater than the sum of their...
• SynergistA substance that enhances the effect of another substance when both are present, even if the synergist itself...
• SyngeneicDescribing individuals or tissues that are genetically identical or sufficiently similar that they do not...
• SyngeneticDescribing a substance or mineral deposit that was formed at the same time as the surrounding rock or matrix...
• SynomoneA semiochemical compound produced by one organism that evokes a behavioral or physiological response in...
• SynophthalmiaA severe congenital malformation characterized by the fusion of the two eyes into a single median eye or a...
• Synoptic scaleA spatial scale in atmospheric chemistry that encompasses phenomena with horizontal dimensions ranging from...
• SynotiaA rare congenital malformation characterized by the fusion of the ears in the midline, often located below...
• Syntectic reactionAn invariant reaction in which two separate liquid phases of different composition react on cooling to give...
• SyntenyThe conserved arrangement of genes on chromosomes between two or more different species, indicating a common...
• Synthetic biopolymerA polymer that is synthesized artificially but possesses structural or functional characteristics similar to...
• Synthetic graphiteA form of graphite produced artificially from carbonaceous precursors, such as petroleum coke or coal tar...
• Synthetic latexA colloidal dispersion of polymer particles in an aqueous medium, produced through emulsion polymerization...
• Synthetic methodA family of solubility measurements that start from a solution of known composition and locate the point...
• SyringomyeliaA chronic neurological disorder characterized by the formation of a fluid-filled cyst, called a syrinx...
• SyrupA concentrated or nearly saturated aqueous solution of a sugar, most commonly sucrose, used as a liquid...
• SystemA specifically defined part of the universe, such as a patient, an organ, or a sample, that is under...
• System of unitsA complete set of units of measurement, including base units and derived units, defined by a consistent set...
• System resolutionThe ability of an analytical instrument or method to distinguish between two closely spaced features in a...
• Systematic effectA consistent and reproducible influence on a measurement result that is not due to random fluctuations. This...
• Systematic errorA component of measurement error that remains constant or varies in a predictable way under specified...
• Systematic examination errorA component of the total examination error that is consistently biased in one direction, leading to results...
• Systematic nameA name for a chemical compound built by applying a formal nomenclature system, so that its parts, assembled...
• Systematic sampleA sample collected by selecting elements from a population at regular intervals, such as every nth item from...
• Systematic samplingA method of selecting samples from a larger population according to a fixed, periodic interval. After a...
• SystematicsThe scientific discipline focused on understanding the evolutionary relationships among organisms and their...
• SystemicRelating to or affecting the entire body or a whole organism, rather than a localized part or a single organ...
• Systemic autoimmune diseaseAn autoimmune disease where the immune system mistakenly attacks multiple organs and tissues throughout the...
• Systemic effectA biological or toxicological effect that occurs in tissues or organs distant from the site of exposure to a...
• Systemic lupus erythematosusA chronic, systemic autoimmune disease characterized by inflammation and tissue damage in multiple organ...
• Systemic sclerosisA chronic autoimmune connective tissue disease characterized by excessive collagen deposition, leading to...
• Systems biologyAn interdisciplinary field that studies biological systems as complex networks of interacting components...
• Szilard-Chalmers effectA nuclear phenomenon where a chemical bond is broken following a nuclear reaction, allowing the newly formed...

1,437 of 13,676 terms in Chemistry terminology (MLC-0109). Request the full dataset.