All articles starting with S

Second voyage of HMS Beagle

The second voyage of HMS Beagle was a Royal Navy hydrographic survey that circumnavigated the globe from 1831 to 1836, commanded by Captain Robert FitzRoy and carrying naturalist Charles Darwin.

Second Wind (entertainment group)

Second Wind is a worker-owned, independent gaming and pop-culture media group founded in November 2023 by the former Escapist video team, including Ben "Yahtzee" Croshaw, known for Fully Ramblomatic, Design Delve, and Adventure is Nigh!.

Second Winter Campaign

The Second Winter Campaign (Ukrainian: Другий зимовий похід), also known as the November Raid, was the final UNR Army operation of the Ukrainian War of Independence, in late 1921.

Second World

Second World: Cold War term for the Soviet-led communist bloc and its allies, the middle category between the capitalist First World and non-aligned Third World; obsolete after 1991, later repurposed for emerging-market economies.

Oct 20, 2026

Second Xiangya Hospital of Central South University

Second Xiangya Hospital of Central South University (中南大学湘雅二医院), founded 1958 in Changsha, a Triple-A tertiary teaching hospital with 3,500 beds; hosts China's National Medical Center for Mental Disorder and leads in psychiatry and endocrinology.

Second-Class Citizen

Second-Class Citizen is a 1974 novel by Nigerian-born writer Buchi Emecheta, following Adah, an Igbo woman who moves to 1960s London and faces racism and sexism.

Second-countable space

A second-countable space, or second axiom of countability, is a topological space with a countable base: every open set is a union of countably many basic open sets.

Second-degree atrioventricular block

Second-degree atrioventricular block (Mobitz I/Wenckebach, Mobitz II, 2:1, high-grade): intermittent failure of AV conduction on ECG; Mobitz II is infranodal, high-risk, and warrants pacing regardless of symptoms.

Second-generation biofuels

Second-generation biofuels are liquid transport fuels made from non-food biomass like crop and forest residues and switchgrass, in contrast to first-generation corn or sugarcane ethanol.

Second-harmonic generation

Second-harmonic generation, also called frequency doubling, is a nonlinear optical process combining two photons into one of twice the frequency, first demonstrated in 1961 with ruby laser light in quartz.

Second-harmonic generation in monolayer transition metal dichalcogenides

Second-harmonic generation in monolayer transition metal dichalcogenides converts light to twice its frequency; broken inversion symmetry in the atomically thin crystals gives a response exceeding bulk forms.

Sep 29, 2026

Second-harmonic generation microscopy

Second-harmonic generation microscopy, also called harmonic generation microscopy, is a label-free nonlinear optical imaging method that visualizes fibrillar collagen and myosin in intact tissue without stains or dyes.

Second-language acquisition

Second-language acquisition (SLA) is the process and research field studying how people learn a language after their first. Covers behaviorist, innatist, interactionist, and sociocultural theories, Krashen's Monitor Model, interlanguage, and age effects on attainment.

Second-life battery

A second-life battery is a lithium-ion pack retired from electric-vehicle service, usually below 70% to 80% of original capacity, and reused in less demanding applications like grid and solar energy storage.

Sep 29, 2026

Second-look surgery

Second-look surgery is a reoperation performed in a patient clinically free of disease after chemotherapy, to detect persistent disease; once routine in ovarian cancer, it was abandoned after trials showed no survival benefit.

Oct 10, 2026

Second-mover advantage

Second-mover advantage is the competitive benefit a firm gains by entering a market after a pioneer, learning from its mistakes and entering once uncertainty is resolved.

Second-order analysis (structural)

Second-order analysis is structural analysis formulated on a structure's deformed geometry, so axial loads on displaced or deflected members produce additional P-delta forces required by design codes like AISC.

Second-order arithmetic

Second-order arithmetic, also called second-order Peano arithmetic, is a formal axiomatic system over natural numbers and sets of them, stronger than Peano arithmetic, weaker than set theory, and the standard framework for reverse mathematics.

Sep 29, 2026

Second-order cone programming

Second-order cone programming (SOCP) is a convex optimization method minimizing a linear function subject to Euclidean-norm constraints, used in portfolio optimization, engineering design, and machine learning.

Second-order logic

Second-order logic is a formal logical system whose quantifiers range over properties, relations, and functions, not just individuals; unlike first-order logic, it can uniquely characterize structures like the natural numbers.

Second-order reaction

A second-order reaction is a chemical reaction whose rate law's exponents sum to two, with rate depending on one concentration squared or the product of two concentrations.

Second-sphere coordination in CO2 reduction catalysts

Second-sphere coordination in CO2 reduction catalysts is the placement of functional groups, ions, or scaffold features beyond the metal's ligands to interact with bound CO2, lowering overpotentials.

Second-system effect

The second-system effect, or second system syndrome, is the tendency of engineers to over-engineer a successful system's successor with deferred features, named by Frederick Brooks in his 1975 book The Mythical Man-Month.

Second-wave feminism

Second-wave feminism, the women's movement of the 1960s to early 1980s following first-wave suffragism, addressed workplace equality, reproductive rights, and domestic life. Key figures include Friedan, Steinem, Beauvoir, and Black feminist critics.

Oct 20, 2026

Second's

Second's (SECOND) is a 9,000 sq ft private event venue on the second floor of the Hotel Eventi at 849 6th Ave, Manhattan, hosting weddings and corporate events with Laurent Tourondel catering, a 30-foot digital billboard, and a retractable roof.

Secondary amenorrhoea

Secondary amenorrhoea (secondary amenorrhea) is the cessation of menses for over 3 months (regular cycles) or 6 months (irregular) after menstruation was established; pregnancy is the most common cause, then functional hypothalamic amenorrhoea and PCOS.

Secondary and therapy-related acute myeloid leukemia

Secondary and therapy-related acute myeloid leukemia is AML arising after a blood disorder, cytotoxic therapy, or inherited predisposition, accounting for about 25 to 30% of new AML diagnoses.

Secondary angle closure glaucoma

Secondary angle closure glaucoma: angle closure from an identifiable underlying disease (neovascularization, uveitis, ICE syndrome, tumors, aqueous misdirection, lens or drug causes) raising IOP and damaging the optic nerve, unlike primary pupillary-block angle closure.