All articles starting with U
6,146 articles
Underlying event
The underlying event (UE) is particle activity in a hadron-hadron collision that accompanies the hard scattering but is not part of it, an unavoidable background to most collider measurements.
Undernutrition in children
Undernutrition in children: insufficient nutrient intake or utilization, manifesting as wasting, stunting, underweight, and micronutrient deficiencies; diagnosed by WHO growth-standard z-scores, linked to about 45% of under-5 deaths, and treated with ready-to-use therapeutic foods.
Underoath
Underoath (UNDERØATH) is an American metalcore/post-hardcore band from Ocala and Tampa, Florida, formed in 1997, known for gold albums They're Only Chasing Safety and Define the Great Line, a 2013 breakup, and the 2018 comeback album Erase Me.
Underpinning
Underpinning is a construction method that deepens a building's foundations by excavating soil beneath them and replacing it with concrete, done in phases to strengthen or deepen inadequate foundations.
Underride guard
An underride guard is a steel barrier on the rear or side of a large truck that stops vehicles from sliding underneath in a crash.
Undersampling (machine learning)
Undersampling is a data-level technique for imbalanced classification that removes majority-class examples to balance training, using controlled methods with a set target size or cleaning methods that remove noisy or borderline examples.
Underscore
Underscore (), Unicode U+005F LOW LINE, formerly SPACING UNDERSCORE: a connector punctuation character from typewriter overstriking, now used as a space substitute in programming identifiers and file names, though Google recommends hyphens in URLs.
Understanding
Understanding is the cognitive achievement of grasping how the parts of a subject relate, so one can explain, predict, and transfer that grasp, and is considered harder to acquire than knowledge.
Understanding by Design
Understanding by Design (UbD) is a curriculum design framework, stated by Grant Wiggins and Jay McTighe in 1998, that plans instruction backward from desired learning outcomes.
Understanding Media
Understanding Media: The Extensions of Man is Marshall McLuhan's 1964 McGraw-Hill book that coined "the medium is the message" and "the global village," arguing media form, not content, reshapes society; reissued by MIT Press in 1994.
Understanding Society (survey)
Understanding Society, the UK Household Longitudinal Study, is an annual household panel survey of the United Kingdom based at the University of Essex since 2009.
Understeer and oversteer
Understeer and oversteer are the two ways a car's cornering deviates from its steering: turning less sharply and running wide, or more sharply with the rear sliding out.
Understory
Understory: the forest vegetation layer beneath the canopy, including shrubs, herbs, ferns, and bryophytes; shaped by overstory light, buffers microclimate, drives regeneration, nutrient cycling, and carbon storage.
Undertale
Undertale (Toby Fox, 2015) is an indie turn-based RPG where killing is optional; FIGHT/ACT/ITEM/MERCY combat, bullet-hell dodging, Neutral/True Pacifist/Genocide endings, $51,124 Kickstarter, ~6.3M Steam sales, Deltarune successor.
Undertale Yellow
Undertale Yellow (UTY) is a free fan-made prequel to Undertale by Team Undertale Yellow, released December 2023 on Game Jolt after seven years, starring Clover, the yellow Justice soul, with pacifist, neutral, and genocide routes.
Undertone (film)
Undertone (stylized undertone), also released as The Undertone, is a 2026 Canadian supernatural horror film and Ian Tuason's feature debut, starring Nina Kiri, sold to A24 after Fantasia 2025 and grossing about $21.5 million on a $500,000 budget.
Undertones of War
Undertones of War is a 1928 First World War memoir by the English poet Edmund Blunden, based on his service as a junior officer on the Western Front.
Undertow (Tool album)
Undertow, Tool's 1993 debut studio album on Zoo Entertainment, an alternative metal record produced by Sylvia Massy with singles "Sober" and "Prison Sex"; it peaked at No. 50 on the Billboard 200, reached No. 19 on a 2019 re-entry, and is certified 3x Platinum by the RIAA.
Undertow (water waves)
Undertow, also called bed return flow, is the wave-driven seaward return flow near the seabed in the surf zone, compensating for the onshore transport by breaking waves.
Undervoltage load shedding
Undervoltage load shedding (UVLS) is an emergency control measure in electric power systems that automatically disconnects selected loads when bus voltages fall below preset thresholds, arresting voltage instability and preventing collapse.
Undervolting
Undervolting is the practice of running a processor or graphics card at a lower voltage than stock to cut heat, power consumption, and fan noise, often without losing performance.
Underwater (film)
Underwater is a 2020 American science-fiction horror film directed by William Eubank and starring Kristen Stewart, whose crew walks across the Mariana Trench floor after an earthquake destroys their drilling station.
Underwater acoustic cloak
An underwater acoustic cloak is a material shell that redirects sound waves around an object, making it undetectable to sonar; the first was demonstrated in 2011.
Underwater acoustic cloaking
Underwater acoustic cloaking is the use of engineered materials to steer sound waves around an object in water, making it difficult to detect with sonar; it remains largely experimental.
Underwater acoustics
Underwater acoustics, also known as hydroacoustics, studies how sound propagates through water and interacts with its boundaries, enabling sonar, ocean navigation, and communication where radio and light cannot reach.
Underwater Compressed Air Energy Storage
Underwater compressed air energy storage (UWCAES) stores high-pressure air on the sea or lake bed, where water pressure keeps it at constant pressure for grid energy storage.
Underwater computer vision
Underwater computer vision is the branch of computer vision that processes underwater images and video, applying detection, classification, segmentation, and reconstruction despite water-induced color casts, haze, and low contrast.
Underwater Demolition Team
Underwater Demolition Teams (UDTs) were U.S. Navy combat-swimmer units formed in 1943 to clear beach obstacles, serving from Saipan and D-Day through the Korean War until absorbed by the Navy SEALs after 1962.
Underwater diving
Underwater diving: descending below the water surface for work, research, or recreation by breath-hold (freediving), scuba, or surface-supplied gas; key hazards are barotrauma and decompression sickness, treated by hyperbaric recompression.
Underwater endoscopic mucosal resection
Underwater endoscopic mucosal resection (UEMR) is an endoscopic technique that removes gastrointestinal lesions by submerging them in water, avoiding submucosal injection, first reported in 2012.