All articles starting with E
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Eta
Eta (Η, η; Greek ἦτα/ήτα), seventh letter of the Greek alphabet, from Phoenician heth. Originally wrote /h/, became long /ɛː/ in Ionic-Attic, then /i/ by iotacism; numeral 8; source of Latin H and Cyrillic И.
ETA (separatist group)
ETA (Euskadi Ta Askatasuna, "Basque Homeland and Liberty") was a Basque separatist terrorist organization founded in 1959 under Franco, seeking an independent Euskal Herria; it killed 853 people, ended armed activity in 2011, and dissolved on 3 May 2018.
Eta and eta-prime mesons
The eta and eta-prime mesons are the two lightest electrically neutral pseudoscalar mesons, with masses of about 548 and 958 MeV, shaped by the axial anomaly of QCD.
Eta Andromedae
Eta Andromedae, officially named Kui by the IAU in 2025, is a spectroscopic binary star of magnitude 4.40 in Andromeda whose two components orbit every 115.72 days.
Eta Aquilae
Eta Aquilae is a classical Cepheid variable star in Aquila, pulsating every 7.18 days; discovered by Edward Pigott in 1784, it was the first Cepheid known.
Eta Aurigae
Eta Aurigae, also called Haedus or Hoedus II, is a blue-white B-type main-sequence star of magnitude 3.17 in Auriga, one of the three Kids asterism stars near Capella.
Eta Boötis
Eta Boötis, also known as Muphrid, is a yellow subgiant star of spectral type G0 IV in Boötes, about 37.2 light-years away, a noted asteroseismic target.
Eta Canis Majoris
Eta Canis Majoris, also named Aludra, is a blue supergiant star of type B5 Ia in Canis Major, the fifth brightest there, about 2,000 light-years away.
Eta Carinae
Eta Carinae (η Carinae) is a supermassive binary star system about 7,500 light-years away in the constellation Carina, briefly the second-brightest star after its 1840s Great Eruption.
Eta Cassiopeiae
Eta Cassiopeiae, also called Achird, is a visual binary star in Cassiopeia about 19.4 light-years from Earth, pairing a Sun-like yellow primary with a fainter orange companion in a roughly 500-year orbit.
Eta Cephei
Eta Cephei is an orange subgiant star of spectral type K0 IV in the constellation Cepheus, about 46.5 light-years from Earth with apparent magnitude 3.41.
Eta Corvi
Eta Corvi (η Crv) is an F-type main-sequence star about 59.6 light-years from Earth in the constellation Corvus, known for its unusual two-belt debris disk.
Eta Funayama Sword Inscription
The Eta Funayama Sword Inscription is a 75-character silver-inlaid text on an iron sword excavated in 1873 from the Eta Funayama Tumulus in Kumamoto Prefecture, Japan.
Eta Hydrae
Eta Hydrae (η Hya) is a blue-white main-sequence star of spectral type B3V in the constellation Hydra, visible to the naked eye at magnitude 4.3.
Eta Kappa Nu
Eta Kappa Nu, also known as IEEE-HKN, is the international honor society of the IEEE, founded in 1904 at the University of Illinois and merged into IEEE in 2010.
Eta Orionis
Eta Orionis is a naked-eye multiple star system of magnitude about 3.35 in Orion, an archetypal quadruple with an eclipsing binary orbited by a third star and a wide fourth.
ETA SA
ETA SA, also known as ETA a.s., is a Czech manufacturer of household appliances, founded in Hlinsko in 1943 and known for vacuum cleaners, irons, and kitchen machines.
Eta Serpentis
Eta Serpentis is an orange giant or subgiant star in the Serpens Cauda section of Serpens, with magnitude 3.25, lying about 60 light years from Earth.
Eta Tauri
Eta Tauri (η Tauri), better known as Alcyone, is a blue giant Be star in Taurus and the brightest member of the Pleiades cluster, at magnitude 2.87.
Eta Ursae Majoris
Eta Ursae Majoris, better known as Alkaid, is a blue-white B-type star marking the tip of the Big Dipper's handle, about 104 light years away.
Eta-mesic nucleus
An eta-mesic nucleus is a hypothetical quasibound state in which an eta meson is held inside a nucleus by the strong interaction alone, predicted by Haider and Liu in 1986.
ETA's 2006 ceasefire declaration
ETA's 2006 ceasefire declaration ("alto el fuego permanente"), announced 22 March 2006, launched a nine-month peace process with Zapatero's government that collapsed with the 30 December 2006 Barajas airport bombing killing two people, formally ending 6 June 2007.
ETABS
ETABS is a structural analysis and design software package for buildings by Computers and Structures, Inc. of California, first released in 1979 and used to model the Burj Khalifa.
Etacelasil
Etacelasil (CGA 13586), an obsolete ethylene-releasing organosilicon plant growth regulator and abscission agent developed by Ciba-Geigy, first reported 1974; not approved in the EU since 2002, with a default MRL of 0.01 mg/kg.
Etaconazole
Etaconazole (CGA 64251, Sonax) is an obsolete triazole-dioxolane fungicide, C14H15Cl2N3O2, that inhibits fungal sterol 14α-demethylase; used against powdery mildew and citrus postharvest rots, now not EU-approved.
Etacystis
Etacystis (Etacystis communis), the H-animal or aitch, an extinct H-shaped soft-bodied invertebrate of uncertain affinity known only from the Pennsylvanian Mazon Creek beds of Illinois; suggested hydrozoan or hemichordate affinities remain unresolved.
Etain Dorsa
Etain Dorsa, a 1,400 km ridge system (dorsa) on Venus at 45 S, 199 E, IAU-approved in 1997 and named for the Irish sun and horse goddess Etain.
Etakkama
Etakkama, also written Aitakkama or Aitukama, was king of Qadesh in Syria during the Amarna period, who began as an Egyptian vassal and defected to the Hittites under Suppiluliuma I.
Étale cohomology
Étale cohomology is a cohomology theory for algebraic varieties and schemes in which étale morphisms act as covers, developed by Grothendieck and Artin to prove the Weil conjectures, completed by Deligne in 1974.
Étale fundamental group
The étale fundamental group, also called the algebraic fundamental group, is an invariant of a scheme introduced by Alexander Grothendieck that classifies its finite étale covers as the topological fundamental group classifies covering spaces.