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Efficacy
Efficacy (pharmacology): a drug's capacity, once receptor-bound, to change target behavior and produce response; distinct from affinity and potency. Spans Ariëns' intrinsic activity, Furchgott's intrinsic efficacy, receptor reserve, inverse agonism, and biased agonism.
Efficiency
Efficiency, in thermodynamics, is the fraction of energy input to a device converted into useful output, defined for a heat engine as work output divided by heat input.
Efficiency (statistics)
Efficiency in statistics measures how well an estimator or statistical test uses sample information, typically by comparing variance against the Cramér–Rao lower bound, the minimum any unbiased estimator can achieve.
Efficiency droop
Efficiency droop is the reduction in a light-emitting diode's efficiency as current density rises, distinct from thermal droop and attributed mainly to Auger recombination and carrier leakage.
Efficiency wage
An efficiency wage is a wage a firm deliberately sets above the market-clearing level because higher pay raises worker productivity by enough to pay for itself, explaining persistent involuntary unemployment.
Efficient energy use
Efficient energy use, or energy efficiency, delivers the same or better energy services, such as light and heat, with less energy, without reducing comfort, through long-lasting technologies.
Efficient estimator
An efficient estimator is an unbiased estimator whose variance attains the Cramér–Rao lower bound, the smallest variance any unbiased estimator can have, making it a minimum-variance unbiased estimator.
Efficient frontier
The efficient frontier is the set of portfolios with the highest expected return for each level of risk, introduced by Harry Markowitz in 1952 in mean-variance portfolio theory.
Efficient-market hypothesis
The efficient-market hypothesis, also called efficient market theory, is the claim that security prices fully reflect available information, so no strategy can systematically beat the market.
EfficientDet
EfficientDet is a family of scalable object detection models from Google Research, introduced at CVPR 2020, using EfficientNet backbones with a bi-directional feature pyramid network and compound scaling.
EfficientNet
EfficientNet is a family of convolutional neural networks for image classification that scales depth, width, and resolution together, reported by Mingxing Tan and Quoc V. Le in 2019.
Effie (musician)
Effie, also known as Kim Na-hyun, is a South Korean singer and rapper known for hyperpop. She won Musician of the Year at the 2026 Korean Music Awards.
Effie Gray
Effie Gray (Euphemia Chalmers Gray, 1828–1897), Scottish artists' model and Lady Millais. Married John Ruskin in 1848, annulled that marriage for non-consummation in 1854, then married John Everett Millais and managed his career.
Effie Gray (film)
Effie Gray is a 2014 British period drama directed by Richard Laxton, written by Emma Thompson, starring Dakota Fanning as Effie Gray, Greg Wise as John Ruskin, and Tom Sturridge as Millais; delayed by two copyright suits, released 2014 UK/2015 US, 108 minutes, mixed reviews.
Effie W. Petersdorf
Effie W. Petersdorf is a transplant physician-scientist at the Fred Hutchinson Cancer Research Center in Seattle whose registry-scale HLA matching studies established the 8/8 match standard for unrelated donor transplantation.
Effigy
Effigy: a material image or likeness of a person, from Latin effigies. Covers funeral and wax effigies (Westminster Abbey, Madame Tussaud tradition) and figures hanged or burned in effigy in protest and ritual.
Effigy mound
An effigy mound is an earthen mound shaped like an animal or spirit figure, built by Indigenous peoples of southern Wisconsin between about AD 650 and 1200.
Effigy Mounds National Monument
Effigy Mounds National Monument is a National Park Service unit in northeastern Iowa preserving more than 200 prehistoric Native American mounds, including 31 bear and bird effigies.
Efflorescence
Efflorescence is the appearance of white salt crystals on the surface of porous materials like brick, concrete, and stone, formed when dissolved salts crystallize as water evaporates.
Effluent
Effluent is wastewater that has been processed or partially processed and released into the environment, from domestic sewage, industrial discharge, or agricultural runoff, and is governed by treatment standards such as US secondary limits.
Efforts to impeach Barack Obama
Efforts to impeach Barack Obama were Republican-led calls during his presidency, peaking in 2014 with Sarah Palin's 'lawless, imperial president' charge and about one-third public support; no inquiry opened and no articles reached the House floor.
Efforts to impeach Donald Trump
Efforts to impeach Donald Trump: House impeachments of December 18, 2019 (abuse of power, obstruction of Congress) and January 13, 2021 (incitement of insurrection), Senate acquittals in 2020 and 2021, and later resolutions.
Effrakata
Effrakata is a 2001 double album by Congolese singer Koffi Olomidé and his orchestra Quartier Latin, a gold-certified set of 16 tracks that won four Kora Awards in 2002.
Effusion cooling
Effusion cooling, also called full-coverage or multi-hole film cooling, protects gas turbine combustor liners and blades by bleeding cooling air through dense arrays of small holes.
Effusion of joint
Effusion of joint (hydrarthrosis, ICD-11 FA36) is increased intra-articular synovial fluid from trauma, degeneration, inflammation, or infection. Diagnosed by ultrasound (~90% sensitive) and arthrocentesis; fluid leukocyte counts classify it, and septic arthritis must be excluded.
Effy Stonem
Effy Stonem, born Elizabeth Stonem, is a fictional character in the British teen drama Skins, played by Kaya Scodelario and featured across two generations of the show.
EFG Hermes
EFG Hermes is an Egyptian investment bank founded in 1984 and now the investment-banking arm of EFG Holding, ranked first in LSEG's 2025 MENA investment banking fees.
EFG International
EFG International is a Zurich-based, SIX-listed Swiss private banking group, one of the industry's "Big 8", known for its portable Client Relationship Officer model and its 2016 acquisition of BSI.
Efgartigimod alfa
Efgartigimod alfa, sold by argenx as VYVGART, is a neonatal Fc receptor blocker that lowers circulating IgG; the FDA approved it in 2021 for generalized myasthenia gravis.
Efi Foufoula-Georgiou
Efi Foufoula-Georgiou is a hydrologist, Distinguished Professor of Civil and Environmental Engineering at UC Irvine, known for multiscale precipitation methods and delta science; she won the International Hydrology Prize in 2023.