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Estimated sign
The estimated sign (℮), also called the e-mark or estimated symbol, is a mark on prepackaged goods certifying that the stated weight or volume was filled under European Union rules.
Estimating equation
An estimating equation sets a function of the unknown parameter and observed data equal to zero; solving it yields the estimate, unifying least squares, maximum likelihood, and method of moments.
Estimating equations
An estimating equation is an equation in an unknown parameter whose solution is the estimate; it generalizes maximum likelihood and needs only the first two moments of the data.
Estimation
Estimation is the branch of statistics that uses sample data to assign values, or ranges of values, to unknown quantities called parameters, such as a population mean.
Estimation of distribution algorithm
An estimation of distribution algorithm (EDA) is a population-based optimization method that learns a probabilistic model of promising solutions and samples new candidates from it.
Estimator
An estimator is a statistic, a rule that computes a number from a random sample, used to estimate an unknown population parameter; the value it produces for one sample is the estimate.
Estradiol Benzoate
Estradiol benzoate is an injectable ester of the estrogen estradiol that acts briefly, with 4 to 5 days of elevated estrogen, and is used mainly in cattle implants.
Estradiol sulfamate
Estradiol sulfamate, also known as E2MATE or PGL2001, is the C3 sulfamate ester of estradiol, developed in the 1990s as an oral estradiol prodrug and potent steroid sulfatase inhibitor.
Estradiol valerate
Estradiol valerate, sold as Delestrogen, is a prodrug ester of the natural estrogen estradiol, used in hormone therapy for menopausal symptoms and hypoestrogenism since 1954.
Estrone
Estrone (E1) is one of the major mammalian estrogens, an aromatized C18 steroid produced by the ovaries, placenta, and adipose tissue, and the first estrogen isolated, crystallized in 1929.
Estrone Sulfate
Estrone sulfate, also called estrone 3-sulfate, is the most abundant circulating estrogen in humans, serving as an inactive reservoir converted to estrone and estradiol in target tissues.
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 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 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 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.
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.
Étale morphism
An étale morphism, or étale map, is a morphism of schemes that is smooth of relative dimension 0, the analog of a local diffeomorphism or covering map in topology.