All articles starting with S

S Normae

S Normae is a classical Cepheid variable star in the southern constellation Norma, the brightest member of the open cluster NGC 6087, pulsating between magnitudes 6.12 and 6.77.

S Pen

The S Pen is a stylus developed by Samsung for its Galaxy phones and tablets, first introduced in 2011 with the original Galaxy Note and built on Wacom's battery-less EMR technology.

S Persei

S Persei is a red supergiant star in the constellation Perseus, a semiregular variable with an 800-day cycle and one of the most luminous members of the Perseus OB1 association.

S Phase (Reactome R-HSA-69242; REACTOME_S_PHASE gene set, 150 genes) is the DNA-synthesis phase of the cell cycle and its curated human pathway, covering replication, Cyclin A:Cdk2 entry events, cohesion, and S-phase checkpoints.

S Saraswathi

S Saraswathi (Telugu: ఎస్. సరస్వతి) is a 2026 Indian Telugu-language courtroom thriller directed by Varalaxmi Sarathkumar in her debut, released in theaters on 6 March 2026.

Oct 3, 2026

S Storm (S风暴)

S Storm (S風暴, 反贪风暴2) is a 2016 Hong Kong crime action film, the second in the Storm series, directed by David Lam and starring Louis Koo as ICAC investigator William Luk probing illegal football betting.

S wave

An S wave, or secondary wave, is a seismic body wave that shakes rock sideways, travels slower than the P wave, and cannot pass through liquids.

S-100

S100 (S-100) protein family: vertebrate-specific dimeric EF-hand calcium-binding proteins, largest EF-hand subgroup, discovered 1965, named for ammonium sulfate solubility, with calcium-switch helix III rotation and S100A10 as the calcium-independent exception.

S-100 (IHO standard)

S-100 is the International Hydrographic Organization's Universal Hydrographic Data Model, a framework of standards for managing and exchanging digital hydrographic data, replacing the older S-57 standard.

S-100 bus

The S-100 bus, also known as the Altair bus, is a 100-line parallel computer expansion bus designed in 1974 for the MITS Altair 8800 and later standardized as IEEE 696-1983.

S-100 Universal Hydrographic Data Model

S-100 is the International Hydrographic Organization's universal hydrographic data model, an 18-part framework based on ISO 19100 that underpins S-10x products like the S-101 chart.

S-125 Neva/Pechora (С-125 «Нева»/«Печора»)

The S-125 Neva/Pechora, NATO SA-3 Goa, is a Soviet short-range surface-to-air missile system adopted in 1961 that still serves dozens of countries and shot down an F-117A over Serbia in 1999.

S-300

The S-300 is a family of Soviet and Russian long-range surface-to-air missile systems developed from the 1960s; the S-300P entered service in 1979 and variants are widely exported.

S-300 missile system

The S-300 (NATO: SA-10 Grumble) is a Soviet and Russian mobile surface-to-air missile system, first fielded in 1978 and exported to more than a dozen countries.

S-400 missile system

The S-400 Triumf, or SA-21 Growler, is a mobile Russian long-range surface-to-air missile system developed from 1993 as an upgrade to the S-300, with a maximum range of 400 km.

S-400 Triumf

The S-400 Triumf (С-400 «Триумф»), NATO reporting name SA-21 Growler, is a Russian mobile surface-to-air missile system developed by Almaz-Antey as successor to the S-300, in service since 2007 and exported to China, India, and Turkey.

S-500

The S-500 Prometey (С-500 «Прометей», Prometheus), designated 55R6M Triumfator-M, is a Russian surface-to-air and anti-ballistic missile system built by Almaz-Antey, designed to intercept ballistic missiles, hypersonic weapons, aircraft, and satellites.

S-500 missile system

The S-500 (С-500 Triumfator-M, marketed as Prometheus) is a Russian long-range surface-to-air and anti-ballistic-missile system developed by Almaz-Antey to supplement the S-400; its first regiment entered combat duty in 2025.

S-520

The S-520 is a Japanese single-stage sounding rocket developed by ISAS to replace the K-9M and K-10, first flown in January 1980 with a 300 km reach.

S-57 (hydrographic data standard)

S-57 is the International Hydrographic Organization's transfer standard for digital hydrographic data, used to exchange data between hydrographic offices and build Electronic Navigational Charts for ECDIS.

S-75 Dvina

The S-75 Dvina, known in the West as the SA-2 Guideline, is a Soviet surface-to-air missile system adopted in 1957 and one of the most widely produced air-defense systems in history.

S-Adenosyl methionine

S-Adenosyl methionine (SAMe, ademetionine) is a naturally occurring coenzyme made from methionine and ATP; the cell's main methyl donor, sold as a supplement and studied for depression, osteoarthritis, and liver disease.

S-Adenosylhomocysteine

S-Adenosylhomocysteine (SAH, also AdoHcy) is an organic sulfide formed as the product of every SAM-dependent methylation reaction in the cell, where it potently inhibits most methyltransferases.

S-adenosylhomocysteine hydrolase deficiency

S-adenosylhomocysteine hydrolase deficiency (AHCY deficiency, SAHH deficiency) is a rare autosomal recessive methionine metabolism disorder causing elevated SAH, SAM, myopathy, liver dysfunction, and developmental delay, with roughly 15 reported cases.

S-Adenosylmethionine

S-Adenosylmethionine (SAM, AdoMet, or SAMe) is a metabolite formed from methionine and ATP that serves as the principal methyl donor in cells, described by Giulio Cantoni in the early 1950s.

S-adenosylmethionine synthetase

S-adenosylmethionine synthetase, or methionine adenosyltransferase (MAT, EC 2.5.1.6), is the only enzyme that makes SAM from methionine and ATP; mammalian MAT I, II, and III isoenzymes from MAT1A, MAT2A, and MAT2B regulate methylation and liver disease.