All articles starting with S

Symmetric matrix

A symmetric matrix is a square matrix that equals its own transpose, with entry i, j equal to entry j, i; all its eigenvalues are real.

Symmetric multiprocessing (SMP) is a computer architecture in which two or more identical processors share one main memory and a single operating system, found in most general-purpose computers today.

Symmetric power

The symmetric power Sym^n(V), or n-fold symmetric power, turns a module V into degree-n homogeneous polynomial expressions in its elements, a quotient of the tensor power that forgets factor order.

Symmetric space

A symmetric space is a Riemannian manifold in which the geodesic symmetry at every point is induced by an isometry, a class introduced and classified by Élie Cartan.

Symmetric tensor

A symmetric tensor is a multidimensional array, the higher-order generalization of a symmetric matrix, whose entries are unchanged by any permutation of their indices, with uses in signal processing and machine learning.

Symmetric-key algorithm

A symmetric-key algorithm, or symmetric cipher, is a cryptographic algorithm that uses a single secret key for both encryption and decryption, as in AES and DES.

Symmetrical components

Symmetrical components decompose unbalanced three-phase voltage or current phasors into positive-, negative-, and zero-sequence sets, a method presented by C. L. Fortescue in 1918 for unbalanced fault analysis.

Oct 21, 2026

Symmetrical intrauterine growth restriction

Symmetrical intrauterine growth restriction (symmetric IUGR, Type I FGR, ICD-11 KA20.11): a growth-restriction pattern where weight, length, and head circumference are all proportionately reduced, starting early in the second trimester, usually from fetal causes such as aneuploidy or congenital infection.

Symmetry

Symmetry is the invariance of an object under a transformation: a snowflake rotated 60° about its center looks exactly as before, a key idea in mathematics and physics.

Symmetry energy

The symmetry energy is the energy cost in nuclear matter of replacing protons with neutrons, defined as the energy difference between pure neutron matter and symmetric matter.

Symmetry group

A symmetry group is the group of all transformations, including rotations, reflections, and translations, that leave a figure, molecule, or crystal pattern unchanged, mapping it onto itself.

Symmetry in biology

Symmetry in biology, also called body symmetry, is the property by which an organism's body divides into equivalent parts, chiefly radial, biradial, and bilateral types in animals.

Symmetry reduction

Symmetry reduction is a model checking technique that identifies states related by symmetries, such as permutations of identical processes, and verifies a smaller quotient structure instead.

Oct 22, 2026

Symmetry verification

Symmetry verification is a quantum error mitigation technique that checks quantum computations against conserved symmetries such as particle number parity and discards runs that violate them.

Symon Petliura (Симон Васильович Петлюра)

Symon Petliura (Симон Васильович Петлюра), Ukrainian statesman, supreme otaman and Directory president 1918–1920, Paris exile leader, assassinated by Scholem Schwarzbard in 1926; acquitted at the 1927 trial.

Oct 22, 2026

Symon Rak-Michajlouski

Symon Rak-Michajlouski (Сымон Рак-Міхайлоўскі, 1885–1938) was a Belarusian politician, publicist, and pedagogue who served in the Rada of the Belarusian Democratic Republic and the Polish Sejm, and was executed during the Stalinist purges.

Symonds Street Cemetery

Symonds Street Cemetery is a colonial-era cemetery in Auckland, in use from 1841 on both sides of Symonds Street, holding an estimated 10,000 burials including Governor William Hobson.

Sympathectomy

Sympathectomy is a surgical procedure that interrupts sympathetic nerves to treat primary hyperhidrosis, facial blushing, and selected cardiac or vascular conditions, with Endoscopic Thoracic Sympathectomy (ETS) being the modern standard.

Sympathetic cooling

Sympathetic cooling is a technique that cools particles without a suitable laser-cooling transition through their mutual interaction with a directly cooled species in the same trap.

Sympathetic detonation

Sympathetic detonation is the initiation of an explosive by the detonation of another explosive in its vicinity, with the impulse transmitted through air, earth, or water; it is a major hazard in ammunition storage and blasting.

Sympathetic magic

Sympathetic magic, also called imitative or homeopathic magic, is the practice of affecting one thing through another by resemblance or past contact, as with hair or images.

Sympathetic nerve block

A sympathetic nerve block is an anesthetic injection near a sympathetic ganglion to test and treat chronic pain, given at the stellate ganglion, lumbar chain, or celiac plexus.

Sympathetic nervous system

Sympathetic nervous system (SNS): thoraco-lumbar autonomic division mediating fight-or-flight, thermoregulation, blood pressure, and skin and muscle innervation, with cholinergic preganglionic and mostly noradrenergic postganglionic neurons.

Oct 20, 2026

Sympathetic neuron

Sympathetic neuron: preganglionic spinal cord (T1–L3) and postganglionic neural crest-derived autonomic neurons mediating fight-or-flight responses; mostly noradrenergic, specified by BMP-driven Phox2b, Mash1, Hand2, Gata3.

Oct 21, 2026

Sympathetic ophthalmia

Sympathetic ophthalmia, also called sympathetic uveitis, is a rare bilateral granulomatous panuveitis triggered by trauma or surgery to one eye, driven by T-cell autoimmunity to exposed ocular antigens, with onset from 5 days to 66 years and corticosteroid plus immunomodulator treatment.

Sympathomimetic drug

Sympathomimetic drugs (adrenergic agonists) mimic epinephrine and norepinephrine, acting directly on adrenergic receptors, indirectly via catecholamine release, or mixed; examples include phenylephrine, ephedrine, amphetamine, and p-synephrine.

Sympathy

Sympathy: other-oriented concern or sorrow for a suffering person, distinct from empathy (feeling with), tied to helping motivation. Covering definition, empathy contrast, Hume/Smith moral theory, and development.

Sympathy for Mr. Vengeance (복수는 나의 것)

Sympathy for Mr. Vengeance (복수는 나의 것, Boksuneun naui geot) is Park Chan-wook's 2002 South Korean film, first of the Vengeance Trilogy, about a deaf laid-off worker whose kidnapping plan for his sister's kidney transplant spirals into a revenge chain.

Sympathy for the Devil

Sympathy for the Devil is a 1968 Rolling Stones song by Jagger and Richards, opening Beggars Banquet. Recorded June 1968 at Olympic Studios, inspired by Bulgakov's The Master and Margarita, filmed by Godard, ranked 32nd on Rolling Stone's 2004 500 list.