Glossary

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Hierarchy of Impairment(also: Hierarchy of Impairments, Disability Hierarchy)

The hierarchy of impairment refers to the phenomenon where certain types of disabilities and impairments are viewed more favorably or given greater attention than others, both by non-disabled people and within the disability community itself. Research by Mark Deal documented how…

High Contrast Mode(also: High Contrast, High Contrast Display)

An operating system or browser display setting that increases the visual distinction between foreground and background elements by using a limited colour palette with strongly contrasting colours, typically black and white or bright colours on dark backgrounds. High contrast…

High-Functioning Autism(also: HFA, HFASD)

A historically used term describing individuals with autism spectrum disorder who have average or above-average intellectual abilities and can communicate verbally. The term is now considered outdated by many in the autism community and clinical practice, with DSM-5 replacing…

High-Stakes Scenarios(also: Safety-Critical Scenarios)

Situations where errors in AI-generated information could lead to significant safety, health, financial, or social consequences. In the context of visual access technology for BLV users, high-stakes scenarios include medication identification (where misreading a dosage could be…

High-Tech AAC(also: Electronic AAC, Speech-Generating Device)

Augmentative and alternative communication systems that use electronic or digital technology to support communication, including speech-generating devices, tablets with AAC software, smartphones with communication apps, and eye gaze systems. High-tech AAC can offer sophisticated…

Higher Education Accessibility(also: University Accessibility, Postsecondary Accessibility)

The policies, practices, accommodations, and technologies that ensure students with disabilities can participate fully and equitably in college and university programs. Higher education accessibility encompasses physical campus access, digital content accessibility, classroom…

Hijax(also: Progressive enhancement with Ajax)

A web development approach coined by Jeremy Keith that applies progressive enhancement principles to Ajax applications. Hijax starts with a fully functional, accessible HTML page and then layers Ajax functionality on top, so that the site degrades gracefully when JavaScript is…

Histogram of Oriented Gradients(also: HOG)

A feature descriptor technique used in computer vision for object detection that counts occurrences of gradient orientations in localized portions of an image. HOG captures edge and texture information by dividing the image into cells and computing gradient direction histograms.…

Hofstede Cultural Dimensions(also: Hofstede’s Cultural Dimensions, Hofstede Model)

A framework by social psychologist Geert Hofstede characterising national cultures along dimensions such as Power Distance, Uncertainty Avoidance, Individualism versus Collectivism, Masculinity versus Femininity, and Time Orientation. It has been used extensively in…

Holistic Accessibility(also: Holistic Approach to Accessibility)

Holistic accessibility is an approach that considers web accessibility not as an isolated technical concern but as one factor within a broader context including usability, user experience, audience characteristics, usage environment, available technologies, and organizational…

HoloLens(also: Microsoft HoloLens)

A self-contained, wearable mixed reality headset developed by Microsoft that overlays interactive holograms onto the user's real-world environment. HoloLens uses spatial mapping, gaze tracking, gesture recognition (air-tap), voice commands, and a physical clicker for…

Home Accessibility Audit(also: Home Safety Assessment, Indoor Accessibility Assessment, HSSAT)

A systematic evaluation of a residential space to identify barriers to access, safety hazards, and opportunities for modification to support people with disabilities, older adults, or families with young children. Audits typically use standardized checklists — such as the Home…

Home Automation(also: Domotics, Smart Home Automation)

The use of technology to automatically control household systems and appliances such as lighting, heating, ventilation, security, and entertainment. Home automation systems use sensors, timers, and programmable rules to operate devices without manual intervention. For people…

Home Button(also: Home Key, Home Screen Button)

The home button is a persistent, consistently-placed control on a device that returns the user to a known starting state — typically the home screen or main menu — from anywhere in the interface. From an accessibility standpoint, the value of a reliable home button is cognitive:…

Home Page Reader(also: IBM Home Page Reader, HPR)

A talking web browser developed by IBM Japan in the late 1990s, designed specifically for blind and low-vision users. Home Page Reader combined a web rendering engine with the ProTalker text-to-speech synthesiser and exposed navigation commands through the numeric keypad,…

Homebound(also: Housebound)

A status in which an individual has difficulty leaving their home without assistive devices or help from others, typically due to illness, injury, or environmental factors such as lack of transportation. As defined by the U.S. Centers for Medicare & Medicaid Services, homebound…

Homomorphic Encryption(also: Partially Homomorphic Encryption, Fully Homomorphic Encryption, FHE)

Homomorphic encryption is a form of encryption that allows computations to be performed on ciphertext (encrypted data) without first decrypting it, such that the result, when decrypted, matches the result of the same operation on the plaintext. In e-voting, homomorphic tallying…

HoneyPage(also: Honey Page)

A purpose-built test web page used by researchers to study the behaviour of browser extensions, crawlers, or malware in a controlled environment. HoneyPages are instrumented to record network requests, JS API calls, and cookies, and are often designed with known accessibility…

Hong Kong Sign Language(also: HKSL)

Hong Kong Sign Language (HKSL) is the primary sign language used by the deaf and hard of hearing community in Hong Kong. It has its own distinct grammar and linguistic rules that differ significantly from spoken Chinese, Cantonese, and other sign languages such as American Sign…

Hornbostel-Sachs Classification(also: Hornbostel-Sachs System, Sachs-Hornbostel)

A comprehensive system for classifying musical instruments based on how they produce sound, originally developed by Erich von Hornbostel and Curt Sachs in 1914. The system divides instruments into four main categories: idiophones (sound from the vibration of the entire…

Hostile Design(also: Hostile architecture, Deterrent design)

A design orientation in which systems — physical, digital, or bureaucratic — are intentionally configured to deter use, discourage certain populations, or reduce uptake, rather than to enable access. Originally applied to urban features like anti-homeless benches and spikes, the…

House-Brackmann Scale(also: H&B Scale, House-Brackmann Grading System)

The House-Brackmann Scale is a clinical grading system used to assess the degree of facial nerve dysfunction in facial palsy. It ranges from Grade I (normal function) to Grade VI (total paralysis), evaluating voluntary movement of the forehead, eye closure, and mouth. While…

Huffman Coding(also: Huffman Algorithm, Huffman Tree)

A data compression algorithm that assigns shorter codes to more frequently occurring symbols and longer codes to less frequent ones, producing an optimal prefix-free encoding. In accessibility and AAC research, Huffman coding has been applied to the design of scanning interfaces…

Human Activity Recognition(also: HAR, Activity Recognition)

A field of machine learning and ubiquitous computing that uses sensor data — typically from accelerometers, gyroscopes, and other sensors in smartphones, smartwatches, or other wearable devices — to automatically identify and classify physical activities performed by a person.…

Human Augmentation(also: Body Augmentation, Augmentative Technology)

Technologies that extend or enhance human physical or cognitive capabilities beyond their current state, including robotic exoskeletons, prosthetic limbs, sensory substitution devices, and brain-computer interfaces. In disability and accessibility contexts, human augmentation…

Human Computation

A computing paradigm in which humans perform tasks that computers cannot yet do reliably, often embedded within systems that combine human and machine capabilities. The classic example is reCAPTCHA, which used human text recognition to digitise books while verifying users were…

Human Computation(also: Crowdsourced Computing)

A computational approach that harnesses human intelligence to perform tasks that computers cannot easily accomplish alone. In accessibility contexts, human computation powers services like remote sighted assistance for blind users, crowd-powered captioning to improve ASR…

Human Cooperation (Accessibility)(also: Cooperative Shared Control)

In the context of accessible gaming and assistive technology, human cooperation refers to arrangements in which a disabled user (the pilot) and another person (the copilot) jointly operate a single system — for example by splitting game controller inputs between two pads so they…

Human Factors Engineering(also: Ergonomics, Human Factors)

The scientific discipline concerned with designing systems, products, and environments to be compatible with the physical and cognitive capabilities and limitations of the people who use them. In accessibility, human factors engineering applies usability methods and techniques —…

Human Failure Modes and Effects Analysis(also: HFMEA, Human FMEA)

An adaptation of Failure Modes and Effects Analysis (FMEA) that focuses specifically on human performance and error. HFMEA systematically examines each step in a process to identify how humans might fail, why they might fail, and what effects those failures would have. In…

Human Infrastructure

A concept from ICT4D (Information and Communication Technologies for Development) research describing the complex web of people, social relationships, environments, and aspirations that shapes how technology is used in a given context. Developed by Sambasivan and Smyth, human…

Human Intelligence Task(also: HIT)

A unit of work on a crowdsourcing platform, particularly Amazon Mechanical Turk, that requires human judgment to complete. HITs typically involve tasks that are difficult for computers but straightforward for humans, such as image labeling, transcription, content moderation, or…

Human Interaction Proof(also: HIP, Human Interactive Proof)

A challenge-response test designed to distinguish human users from automated software (bots). Human Interaction Proofs are the technical term for CAPTCHAs and similar verification systems. While effective against automated attacks, HIPs present significant accessibility…

Human Interface Device(also: HID, Input Device, Peripheral)

Any device used to facilitate interaction between a human and a computer, including keyboards, mice, trackballs, joysticks, touchscreens, switches, and eye-tracking systems. The USB HID standard defines a protocol for these devices that enables plug-and-play compatibility. For…

Human Machine Interface(also: HMI, Human-Computer Interface)

The point of interaction between a human user and a machine, encompassing all hardware and software through which users control and receive feedback from a system. In accessible design, HMIs must support multiple modalities—visual, auditory, and haptic—to accommodate users with…

Human Rights Model of Disability(also: Rights-Based Model of Disability)

A framework for understanding disability that builds on and extends the social model by emphasising the inherent dignity and rights of people with disabilities. Grounded in the UN Convention on the Rights of Persons with Disabilities (CRPD), this model goes beyond identifying…

Human-AI Alignment(also: AI Alignment, Value Alignment)

The design and training of AI systems to exhibit behaviours consistent with human values, intentions, and goals. In accessibility, human-AI alignment requires that AI systems accurately represent and respond to the diverse values and experiences of disabled and neurodivergent…

Human-AI Co-Creation(also: Human-AI Co-Creative, Co-Creative AI, Mixed-Initiative Co-Creation)

Human-AI co-creation refers to creative work in which a person and an AI system iteratively contribute to the same artifact, with each shaping the other's next move rather than the AI acting as a one-shot tool. In accessibility contexts, co-creative systems are used to scaffold…

Human-AI Collaboration(also: Human-AI Teaming, AI-Assisted Authoring)

An interaction paradigm where humans and artificial intelligence systems work together, each contributing their complementary strengths to achieve outcomes neither could produce as effectively alone. In accessibility contexts, human-AI collaboration combines AI efficiency in…

Human-AI Interaction(also: HAI, Human-AI Collaboration, AI Interaction Design)

The study and design of how people interact with artificial intelligence systems, including how AI communicates its outputs, uncertainty, and limitations to users. Key principles include making AI behavior transparent, supporting user correction of errors, acknowledging…

Human-Centered AI(also: HCAI, Human-Centered Artificial Intelligence, HCXAI)

Human-Centered AI (HCAI) is a design and research orientation that places human experience, context, agency, and values at the center of how AI systems are built and evaluated, rather than optimizing only for model performance. In accessibility contexts, HCAI emphasizes that AI…

Human-Centered Computing(also: Human-Centred Computing, People-Centered Computing)

Human-centered computing is an approach to technology design and development that places human needs, capabilities, and experiences at the center of the design process. It emphasizes understanding the full diversity of human physical, sensory, and cognitive abilities, and…

Human-Centered Design(also: HCD, User-Centered Design, UCD)

A design approach that prioritizes the needs, capabilities, and experiences of end users throughout the design process. Popularized by IDEO and formalized in ISO 9241-210, human-centered design involves iterative cycles of understanding user context, specifying requirements,…

Human-Centered Threat Modeling

A methodology borrowed from security and privacy research that identifies the people and institutions who intend to cause harm to a specific population, the threats they pose, and the defensive strategies the population uses. In accessibility research, human-centered threat…

Human-Machine Interface(also: HMI, Human-Computer Interface)

The point of interaction between a human user and a machine, system, or device, encompassing the hardware and software through which users communicate with and control technology. In the context of accessible design, HMIs include physical controls (buttons, levers, keypads),…

Human-Nature Interaction(also: HNI)

A research area within human-computer interaction concerned with how people perceive, access, and engage with natural environments, and how technology can mediate that relationship. HNI draws on environmental psychology, biophilia, and posthumanist design to study experiences…

Human-Powered Accessibility(also: Human Computation for Accessibility, Crowd-Powered Assistive Technology)

An approach to assistive technology that uses remote human workers — whether paid crowdworkers, volunteers, or trained agents — to provide accessibility services that automated systems cannot yet deliver reliably. Examples include providing real-time visual descriptions for…

Human-Robot Interaction(also: HRI)

The interdisciplinary field studying how humans and robots communicate, collaborate, and coexist. In accessibility contexts, HRI research explores how robots can be designed to support people with disabilities in workplaces, homes, and public spaces — including collaborative…

Human-Vehicle Interaction(also: HVI, Vehicle-pedestrian interaction)

The field studying how people communicate, negotiate, and coordinate with vehicles and their occupants — including drivers, passengers, and, increasingly, automated systems. Human-vehicle interaction encompasses internal interfaces (dashboards, voice assistants,…

Human-computer interaction(also: HCI, Human-machine interaction)

The interdisciplinary study of the design, evaluation, and use of interactive computing systems by humans, drawing on computer science, psychology, design, and social science. HCI research encompasses how people use technology, how interfaces should be designed for usability and…