Technology glossary

Apparent Magnitude

A scale astronomers use to measure how bright an object appears from Earth, where lower numbers mean brighter, and each five-step drop represents a hundredfold increase in brightness.

Aptamer

An aptamer is a short DNA or RNA sequence that folds into a structure capable of binding a chosen molecular target. Researchers select or design aptamers for molecular recognition, sensing and therapeutic research. Binding in a laboratory assay does not by itself establish clinical effectiveness.

Aqueous Alteration

Chemical and mineralogical changes that occur when liquid water interacts with rock, dust, or other solid material. In meteorites and planetary bodies, these changes can reveal the past presence, temperature, and chemistry of water.

Aqueous Zinc-Iodine Battery(AZIB)

A rechargeable battery that uses zinc and iodine as active materials with a water-based electrolyte. The chemistry can reduce flammability compared with batteries using organic electrolytes, but iodine migration, zinc corrosion and scale-up remain important engineering challenges.

Area Under the Receiver Operating Characteristic Curve(AUROC)

A threshold-independent measure of how well a scoring model ranks positive cases above negative cases. A value of 0.5 corresponds to random ranking, while 1.0 represents perfect separation.

Arrhythmia

An abnormal heart rhythm, such as beating too fast, too slow, or irregularly, which can be harmless or a sign of an underlying heart problem.

Artificial Light at Night(ALAN)

Outdoor or indoor light produced by human technology during naturally dark hours. Its brightness, direction, timing, and spectrum can alter sleep, navigation, feeding, reproduction, and ecological interactions in humans and wildlife.

Artificial Skyglow

The brightening of the night sky caused by artificial light scattered in the atmosphere. It can extend far beyond cities, obscure faint stars, disrupt ecosystems and human sleep patterns, and reduce the quality of astronomical observations.

Assembloid

A laboratory model made by joining two or more organoids so researchers can study how different tissue regions connect, migrate and signal to one another.

Assigned Representative(AR)

A person authorized to act for a manufacturer inside an electronic regulatory process. In ENISA's reporting platform, assigned representatives register the organization, submit notifications and manage follow-up information.

Assisted GPS(A-GPS)

Assisted GPS (A-GPS) combines satellite positioning with information supplied by a mobile network or other data connection, helping a phone locate satellites and calculate its position faster, especially when signals are weak.

Assistive Dressing Device

A tool or robotic system designed to help a person put on or remove clothing when mobility, strength, coordination, or reach is limited. It may provide physical guidance, gripping, positioning, or automated assistance while prioritizing comfort and safety.

Astronomical Light Pollution

Artificial light that interferes with observing the night sky by increasing background brightness, creating glare, or producing moving trails and reflections. Sources include outdoor lighting, illuminated structures, aircraft, and satellites.

Asymmetric Autocatalysis

Asymmetric autocatalysis is a reaction in which a chiral product accelerates the formation of more product with the same handedness. Repeated cycles can amplify a very small initial imbalance between enantiomers into a strongly one-sided mixture.

Asymmetric Synthesis

Asymmetric synthesis is a chemical strategy that preferentially produces one enantiomer of a chiral compound rather than an equal mixture of both. It often uses a chiral catalyst, reagent or starting material to guide the three-dimensional outcome.

Asynchronous Robot Control

Asynchronous robot control is a control approach in which sensing, computation, and physical motion overlap in time instead of occurring as a strictly sequential cycle, reducing idle pauses between actions.

Atlantic Meridional Overturning Circulation(AMOC)

A large system of Atlantic Ocean currents that carries warm surface water north and colder, denser water back south at depth, redistributing heat and helping keep Western Europe's climate relatively mild.

Atmospheric Escape

The loss of atmospheric gases from a planet into space.

Atmospheric Neutrino

A neutrino created when cosmic rays strike atoms in Earth's atmosphere. Atmospheric neutrinos are scientifically useful but also form a background for searches for neutrinos from distant astrophysical sources.

Atmospheric Predictability

The degree to which the future state of the atmosphere can be estimated from its present state. It is limited by observation errors, imperfect models and the atmosphere's chaotic behavior, which causes small uncertainties to grow over time.

Atmospheric Spectroscopy

The analysis of how an atmosphere absorbs, emits, or scatters light at different wavelengths to infer its composition, temperature, pressure, clouds, and motion. It is used to study Earth, Solar System bodies, and exoplanets.

Atomic Clock

An atomic clock measures time using the stable resonance frequency of atoms. GPS satellites carry atomic clocks because tiny timing errors translate directly into large positioning errors for receivers on Earth.

Attack Chain

The connected sequence of steps used to reach a cyber objective, such as gaining access, exploring systems, escalating privileges and acting on data. Breaking any stage can prevent later actions even when an attacker has already completed earlier ones.

Attack Path

An attack path is the sequence of weaknesses, permissions, credentials, systems, and trust relationships an attacker can chain together to move from an initial foothold toward a target.

Attack Surface

All reachable devices, accounts, software and connections that an attacker could potentially use to enter or influence a system.

Auscultation

Listening to the heart or lungs with a stethoscope, digital or acoustic, to detect abnormal sounds like murmurs or irregular rhythms.

Authorization Boundary

A rule that separates actions a user or system has explicitly permitted from actions that require additional approval. For AI agents, an authorization boundary can cover payments, account creation, form submission, credential use, data access, or changes to external systems. A technically possible action is not necessarily authorized.

Automated Ball-Strike System(ABS)

A pitch-tracking system that compares a baseball's path with a computed strike zone. In challenge mode, a human umpire makes the original call and an eligible player may request an electronic review.

Automated Employment Decision

An employment-related decision or recommendation made or substantially assisted by an automated system, such as screening applicants, ranking candidates, assigning work, evaluating performance, setting pay, or selecting workers for promotion or dismissal. Applicable legal definitions vary by jurisdiction.

Automated Guided Vehicle(AGV)

A mobile industrial machine that transports materials along planned routes using guidance and control systems. Unlike a general-purpose robot, an AGV is usually designed for repeatable logistics tasks within controlled environments such as factories and warehouses.