Glossary

Search results

Head Tracking(also: Head Movement Tracking, Head-Controlled Input, Head Tracker)

An assistive technology input method that translates natural head movements into computer cursor control or other input actions. Head tracking systems use cameras, infrared sensors, or depth sensors to detect head position and orientation, allowing users with limited or no hand…

Head Wand(also: Head Pointer, Head Stick, Mouth Stick)

A head wand is an assistive input device consisting of a pointer attached to a headband or held in the mouth, allowing people with limited or no hand and arm function to operate a keyboard, touchscreen, or other controls using head movements. Head wands are commonly used by…

Head-Mounted Display(also: HMD, VR Headset, AR Headset)

A wearable device worn on the head that places a display in front of the user's eyes to present virtual or augmented content. HMDs range from fully immersive VR headsets (like Meta Quest) that replace the visual environment to AR glasses that overlay digital information on the…

Head-Mounted Display (HMD)(also: HMD, Head-Mounted Display, Smart Glasses)

A display device worn on the head that places visual content in front of one or both eyes. Head-mounted displays include AR smart glasses (like Vuzix Blade), VR headsets, and mixed reality devices. In accessibility applications, HMDs can present captions, sign language…

Head-based Pointing(also: Head Tracking, Head Mouse, Head-controlled Input)

An alternative input method that allows users to control an on-screen cursor by moving their head, typically tracked via a camera, infrared sensor, or inertial measurement unit. Head-based pointing is particularly valuable for people with motor impairments who cannot use…

Head-mounted display(also: HMD, Smart glasses, Head-worn display)

A wearable device that positions a display in front of one or both eyes, either overlaying digital content onto the real world (optical see-through) or replacing the visual field with a camera-captured and digitally processed view (video see-through). For people with low vision,…

Head-related transfer function(also: HRTF)

A response function that describes how sound from a specific point in space is filtered by the shape of the outer ear, head, and torso before reaching the eardrum. HRTFs are unique to each individual and are used in spatial audio rendering to create realistic 3D sound over…

HeadMaster(also: HeadMaster Plus)

An early head-pointing assistive technology device developed by Prentke Romich Company that translates head movements into mouse cursor movements on screen. The HeadMaster uses an ultrasonic sensor worn on the head (typically mounted on a headband or glasses) to track head…

Heading Navigation(also: Navigate by Headings)

A screen reader navigation strategy that allows users to jump between heading elements (h1-h6) on a webpage, bypassing intermediate content to quickly find sections of interest. Heading navigation is one of the most important strategies for efficient screen reader use, but its…

Heading Structure(also: Header Hierarchy, Heading Levels, Document Outline)

The hierarchical organization of headings (H1 through H6 in HTML) used to define the logical structure and sections of a document or web page. Proper heading structure is one of the most critical accessibility features for screen reader users, who rely on headings to skim…

Heading hierarchy(also: Heading structure, Heading levels)

The logical, nested structure of HTML heading elements (h1 through h6) that organizes web content into a navigable outline. A well-structured heading hierarchy uses heading levels sequentially without skipping levels, with a single h1 for the page title, h2 for major sections,…

Heading hierarchy(also: Heading structure, Heading levels, Document outline)

The logical structure created by using HTML heading elements (h1 through h6) in a nested, hierarchical order to convey the organisation of content on a web page. A proper heading hierarchy starts with a single h1 for the page title, with h2 elements for major sections, h3 for…

Heads-Up Display(also: HUD)

A transparent or overlay display that presents information in the user's direct line of sight without requiring them to look away from their current viewpoint. Originally developed for aviation, HUDs are widely used in virtual and augmented reality to attach interface elements —…

Health Data Visualization(also: Health Data Display, Patient Data Visualization)

The presentation of personal health information — such as blood glucose levels, blood pressure readings, activity data, or medication schedules — in visual formats including graphs, charts, trend lines, and indicators designed to help patients understand and manage their health…

Health Informatics(also: Medical Informatics, Clinical Informatics)

The interdisciplinary field concerned with the design, development, and use of information technology and systems to improve healthcare delivery, management, and outcomes. Health informatics encompasses electronic health records, clinical decision support systems, patient…

Health Literacy(also: Digital Health Literacy, eHealth Literacy)

The degree to which individuals can obtain, process, understand, and act on health information and services needed to make appropriate health decisions. In the digital context, health literacy extends to the ability to seek, find, understand, and appraise health information from…

Health Misinformation(also: Medical Misinformation, Health Disinformation)

False or misleading health-related information that is spread regardless of intent to deceive. On social media and video platforms, health misinformation about conditions like ADHD can include inaccurate symptom descriptions, unproven treatments, misleading diagnostic criteria,…

Health Monitoring(also: Remote Patient Monitoring, Health Surveillance)

The continuous or periodic collection of health-related data using sensors, wearables, or smart home technology to track an individual's wellbeing and detect problems. Health monitoring systems may track vital signs (heart rate, blood pressure), activity levels, medication…

Health-Related Impairment and Disability(also: HIID, Health-Related Impairments and Disabilities)

A category of impairments that arise as a consequence of health conditions, both chronic and acute, rather than from a traditionally defined disability. HIIDs are characterized by four properties: they are combinatorial (multiple low-intensity impairments that interact to create…

Healthcare Access(also: Healthcare Accessibility)

The ability of disabled people to obtain timely, appropriate, and respectful healthcare services. Healthcare access barriers include physical inaccessibility of medical facilities, communication barriers with providers, diagnostic overshadowing (where symptoms are attributed to…

Hearable(also: Smart Earbud, Smart Earphone)

A class of in-ear or over-ear wearable devices that combine audio playback with one or more sensors and on-device computing - microphones for ambient audio capture, inertial sensors, biosensors, and machine-learning accelerators - enabling features beyond passive listening.…

Hearcon(also: 3D Earcon)

An extension of the earcon concept that adds three-dimensional spatial audio properties to non-speech audio cues used in computer interfaces. While earcons are abstract synthesized sounds that represent interface events or objects, hearcons position these sounds in 3D space…

Hearing Aid(also: Hearing Aids)

An electronic device worn in or behind the ear that amplifies sound to assist people with hearing loss. Modern hearing aids include digital signal processing, directional microphones, and connectivity features like Bluetooth. While hearing aids improve access to speech and…

Hearing Aid(also: HA, BTE, Behind-the-Ear)

An electronic device worn in or behind the ear that amplifies sound for individuals with hearing loss. Modern hearing aids include features such as Bluetooth connectivity, directional microphones, and noise reduction. Behind-the-ear (BTE) models are among the most common styles.…

Hearing Aid Compatibility(also: HAC, HAC Rating)

Federal Communications Commission (FCC) requirements and ratings for telephones to work effectively with hearing aids and cochlear implants. HAC standards address acoustic coupling (how well the phone works with hearing aid microphones) and telecoil coupling (magnetic signal…

Hearing Impairment(also: Hearing Loss, Hard of Hearing)

A partial or total inability to hear sounds in one or both ears, ranging from mild to profound. Hearing impairment can be congenital or acquired, and may worsen with age (presbycusis). In digital accessibility, hearing impairment necessitates alternatives to audio content such…

Hearing Loss(also: Hearing Impairment, Hard of Hearing, Deafness)

A partial or total inability to hear sounds, ranging from mild hearing loss to profound deafness. Hearing loss can be congenital or acquired, and becomes increasingly common with age, affecting approximately one-third of people over 65. Digital accessibility for people with…

Hearing loss(also: Hearing impairment, Hard of hearing, Deafness spectrum)

A reduction in the ability to perceive sounds, occurring on a spectrum from mild (difficulty hearing soft sounds or speech in noisy environments) through moderate and severe to profound (inability to hear most sounds without amplification). Hearing loss may be unilateral (one…

Heart Rate Variability(also: HRV)

The variation in time intervals between consecutive heartbeats, reflecting the balance between sympathetic (stress response) and parasympathetic (rest and recovery) branches of the autonomic nervous system. HRV is used as an objective measure of stress, emotional state, and…

Heat Map(also: Heatmap, Attention Map, Gaze Map)

A data visualization technique that uses colour intensity to represent the distribution and density of user attention or interaction on a page or interface. In eye tracking research, heat maps aggregate fixation data from multiple users, with warmer colours (red, orange)…

Heavy Disguise

A research-ethics technique introduced by Amy Bruckman (2002) for handling quotes and user-generated content drawn from public online spaces. Under heavy disguise the researcher rephrases quotations, omits usernames and platform identifiers, and verifies (e.g., via search) that…

Height-Field Surface(also: Surface plot, Heightfield plot, 2.5D surface)

A type of 3D data visualisation in which a scalar value (for example, elevation, intensity, pressure, or probability) is plotted over a two-dimensional domain, producing a continuous surface that can be rendered as a mesh, contour map, or draped cloth. Height-field surfaces are…

Heisenberg Effect(also: Heisenberg Problem)

In human-computer interaction, a spatial interaction problem where the act of making a selection disrupts the positional accuracy of the cursor or pointer. In virtual reality freehand gesture contexts, the Heisenberg effect occurs when the physical movement required to confirm a…

Help America Vote Act(also: HAVA)

The Help America Vote Act (HAVA) is a United States federal law enacted in 2002 in response to the voting irregularities of the 2000 Presidential Election. HAVA established mandatory minimum standards for states in key areas of election administration, including requirements…

Help-Seeking(also: Help seeking behavior)

The deliberate process of asking for, searching for, or otherwise obtaining assistance to complete a task, learn a feature, or resolve a breakdown. In accessibility contexts, help-seeking is often shaped by inaccessible documentation, visually oriented tutorials, and the cost of…

Hemi-Attention(also: Hemispatial Neglect, Unilateral Neglect, Visual Neglect)

A neurological condition in which a person has reduced attention or awareness to one side of space, typically the side opposite to a brain injury. Unlike hemianopsia (where visual input is lost), hemi-attention involves a failure to attend to or process stimuli on the affected…

Hemianopsia(also: Hemianopia, Half-Field Vision Loss)

Loss of vision in one half of the visual field in one or both eyes, typically caused by damage to the brain's visual pathways rather than the eyes themselves. The most common form is homonymous hemianopsia, where the same half of the visual field is lost in both eyes — for…

Hemiparesis(also: Hemiplegia, One-Sided Weakness)

Weakness or partial paralysis affecting one side of the body, commonly resulting from stroke, traumatic brain injury, or neurological conditions. Hemiparesis affects motor control, coordination, and strength in the arm, leg, and sometimes face on the affected side. People with…

Hemiplegia(also: Hemiparesis)

A condition involving paralysis or severe weakness on one side of the body, most commonly resulting from stroke but also caused by traumatic brain injury, cerebral palsy, or other neurological conditions. Hemiplegia affects the arm, leg, and sometimes facial muscles on the…

Hemiplegia(also: Hemiparesis)

Paralysis or severe weakness affecting one side of the body, typically caused by stroke, cerebral palsy, or brain injury. Hemiplegia commonly affects the arm, leg, and sometimes face on either the left or right side. For digital accessibility, users with hemiplegia may operate…

Hermeneutical Injustice

Hermeneutical injustice, a concept developed by philosopher Miranda Fricker, is a form of epistemic injustice in which a person's experience is unintelligible to themselves or others because the collective interpretive resources of their community lack the concepts, vocabulary…

Heuristic Evaluation(also: Expert Review, Heuristic Review)

A usability inspection method in which a small group of expert reviewers evaluate a user interface against a set of established design principles or heuristics. Originally developed by Jakob Nielsen, the method is widely used in accessibility assessment where experts review…

Heuristic Evaluation(also: Expert Review, Heuristic Review)

An accessibility or usability evaluation method in which evaluators examine an interface against a set of recognised principles (heuristics) to identify potential problems. In web accessibility, heuristic evaluation typically involves checking pages against WCAG success criteria…

Heuristic Transcoding(also: Rule-based Transcoding)

Heuristic transcoding is the automated transformation of web content to improve accessibility, device compatibility, or readability using a fixed set of predefined rules that inspect the page structure, media types, or visual characteristics — for example, rules that strip small…

Heuristic Walkthrough(also: Heuristic walk-through)

A usability evaluation method proposed by Andrew Sears (1997) that combines scenario-based cognitive walkthrough with heuristic evaluation. Evaluators work through realistic user tasks using a prioritised list of heuristics, surfacing both task-specific and general usability…

Heuristic evaluation(also: Expert review, Usability inspection)

A usability and accessibility evaluation method where trained evaluators systematically assess an interface against a set of recognized principles or guidelines (heuristics) to identify potential problems. In accessibility contexts, heuristic evaluation applies principles from…

Hick-Hyman Law(also: Hick's Law)

A principle from experimental psychology stating that the time it takes a person to make a decision increases logarithmically with the number of available choices. In accessibility and interface design, Hick-Hyman Law informs the practice of limiting the number of options…

Hidden Labour of Disability(also: Invisible Work of Disability, Disability Labour)

The unrecognized time, effort, and energy that disabled people must invest to navigate inaccessible environments, use assistive technologies, manage care relationships, and participate in activities that non-disabled people can do with minimal effort. Examples include spending…

Hidden Markov Model(also: HMM)

A statistical model used extensively in pattern recognition where the system being modeled is assumed to follow a Markov process with hidden (unobserved) states. HMMs have been foundational in both automatic speech recognition and sign language recognition, as they can model…

Hierarchical Task Analysis(also: HTA)

A structured method for describing and analyzing tasks by breaking them down into goals, sub-goals, and operations in a hierarchical tree structure. Originally developed for industrial and safety-critical domains, HTA has been adopted in accessibility research to identify where…