Technology Glossary

Ground Control Segment

The ground control segment is the terrestrial part of a satellite navigation system that tracks satellites, estimates their orbits and clock errors, monitors system health and uploads updated navigation data.

Ground Delay Program(GDP)

An air traffic management programme that holds selected flights at their departure airports when demand is expected to exceed capacity at a destination. Delaying aircraft on the ground is generally safer and more efficient than making them wait in the air.

Grounding Line

The boundary where an ice sheet stops resting on bedrock and begins floating as an ice shelf, a critical zone for measuring discharge and instability.

Gut Microbiome

The community of microorganisms and their genes living in the digestive tract.

Gut Microbiota

The community of bacteria, archaea, fungi, viruses and other microorganisms living in the digestive tract. Microbiota refers to the organisms, while microbiome can also include their genes and surrounding environment.

Habitable Zone

The range around a star where temperatures may allow liquid water on a planet's surface under suitable atmospheric conditions.

Haptic Feedback

Information communicated to a user through the sense of touch, using forces, vibrations, motion, or changes in surface texture. It can confirm an action, simulate contact, or convey physical properties in phones, vehicles, robots, medical devices, and virtual environments.

Hard Coral Cover

The percentage of a surveyed seafloor area occupied by living reef-building corals with calcium carbonate skeletons. It is a widely used indicator of reef condition, but it does not capture species composition, fish abundance or structural complexity.

Hardware Abstraction Layer

A software layer that provides a common interface while hiding differences between underlying hardware systems.

Hazard Ratio(HR)

A statistic comparing how quickly an event such as death or disease progression occurs over time in two groups. A value below 1 indicates a lower event rate in the treatment group during follow-up.

Heart Rate Variability(HRV)

The variation in time between successive heartbeats. It reflects influences from the autonomic nervous system and is used in research and sports monitoring, but readings depend on measurement quality, activity, illness and individual context.

Heat Load

The amount of heat introduced into a cooled system that the refrigeration stage must remove.

Heat Shock Factor 1 (HSF1)

A protein cells normally produce in response to heat or physical stress, which some cancer cells co-opt to adjust their internal chemistry and match the surrounding tumor conditions.

Hepatitis B surface antigen(HBsAg)

A protein on the surface of hepatitis B virus particles. Its presence in blood is used to identify infection, and quantitative levels can help assess disease activity and eligibility for some treatments.

High-Energy Astrophysical Neutrino

A neutrino produced by an energetic source beyond Earth's atmosphere, such as an active galactic nucleus or another cosmic particle accelerator. Its energy and arrival direction can carry information about the source.

High-Performance Computing(HPC)

The coordinated use of powerful processors, fast networks and storage to solve computational problems too large or slow for an ordinary computer.

High-Risk AI System

An AI system used in a context where failure or misuse could seriously affect safety or fundamental rights, as defined by applicable regulation. Such systems may face stricter requirements for risk management, data, documentation, oversight, accuracy and security.

Homochirality

Homochirality is the dominance of one molecular handedness within a system. Biology is strongly homochiral: proteins mostly use amino acids of one handedness, while DNA and RNA use sugars of the opposite conventional handedness.

Host Factor

A molecule produced by a host cell that a pathogen uses to enter, replicate, or spread.

Hot Isostatic Pressing(HIP)

A manufacturing process that applies high temperature and uniform gas pressure to densify powders or remove internal pores from metal components.

Human-AI Co-Design

A design process in which people and AI systems iteratively contribute ideas, alternatives, evaluations, or refinements. Humans retain responsibility for goals, constraints, context, and final decisions, while AI can expand exploration or automate parts of the workflow.

Human-in-the-Loop AI

An artificial intelligence workflow in which people review, guide, label, approve, or correct parts of a model's operation. Human involvement is often used to improve training data, handle uncertain cases, and provide oversight for consequential decisions.

Human-in-the-Loop System(HITL)

An automated system that requires a person to review, approve or override important outputs before they become final actions.

Human-Machine Interface(HMI)

A human-machine interface is the set of controls, displays, and feedback channels through which a person monitors and operates a machine or industrial system.

Human-on-the-Loop

A supervision model in which an autonomous system, such as an AI flight-control agent, performs a task while a human can monitor it and intervene or take back control at any moment.

Humanoid Robot

A robot with a body plan resembling a person, usually including a torso, head, arms and two legs. The form is intended to help the machine use spaces and tools designed for people, but human-like appearance does not imply human-level intelligence or dexterity.

Hybrid Quantum-Classical Computing

A computing model in which a quantum processor handles selected subproblems while conventional CPUs or GPUs manage data preparation, control and the rest of the workload. The useful division of work depends on algorithms and measured system performance.

Technology glossary