Glossary

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Amazon Alexa(also: Alexa, Echo)

A cloud-based voice assistant developed by Amazon, available on Echo smart speakers, Echo Show smart displays, and third-party devices. Users interact with Alexa through wake-word-activated voice commands to perform tasks such as setting reminders, playing music, controlling…

Amazon Mechanical Turk(also: AMT, MTurk, Mechanical Turk)

A crowdsourcing marketplace operated by Amazon that enables individuals and businesses to distribute tasks (called Human Intelligence Tasks or HITs) to a distributed workforce who complete them remotely for small payments. AMT has been widely used in HCI and accessibility…

Ambient Audio(also: Ambient Sound, Environmental Audio, Background Audio)

The background sound of an environment — voices, traffic, water, wind, music, birdsong — captured incidentally rather than as the main focus of a recording. In accessible photography and audiophotography tools, ambient audio is often recorded automatically in the seconds leading…

Ambient Display(also: Ambient Interface, Peripheral Display)

A display or interface that communicates information through subtle environmental changes — such as colour shifts, lighting changes, or gentle sounds — that can be perceived at the periphery of a user's attention without demanding direct focus. In accessibility contexts, ambient…

Ambient Intelligence(also: AmI)

An environment enriched with networked, sensor-equipped devices that are sensitive and responsive to the presence and needs of people within it. Ambient intelligence systems anticipate user requirements by learning preferences and behaviours over time, and adapt their responses…

Ambient assisted living(also: AAL, Smart home assistive living)

Technology systems embedded in the home environment — including sensors, microphones, and smart devices — that monitor and support older adults or people with disabilities to live independently and safely. AAL aims to detect emergencies like falls, remind about medications, and…

Ambiguous Loss

Ambiguous loss, a concept articulated by Pauline Boss, is 'a situation of unclear loss that remains unverified and thus without resolution'. Boss distinguishes two types: physical loss where someone is 'gone, but not for sure' (for example, a missing person) and psychological…

Ambiguous keyboard(also: T9 input, Multi-tap disambiguation)

A text entry method in which multiple letters are mapped to each physical key, requiring disambiguation algorithms (typically dictionary-based) to determine the intended word from the sequence of key presses. Originally popularized by T9 predictive text on mobile phone numeric…

Ambisonics(also: Ambisonic audio, Ambisonic sound)

A full-sphere surround sound technique that captures and reproduces audio from all directions — including above and below the listener — using a spherical harmonic representation of the sound field. Originally developed by Michael Gerzon in the 1970s, ambisonics differs from…

Amblyopia(also: Lazy eye)

A neurodevelopmental vision disorder in which one eye has reduced visual acuity that cannot be fully corrected with glasses or contact lenses, caused by abnormal visual development in early childhood. The brain favors one eye and partially suppresses input from the weaker eye,…

American Sign Language(also: ASL)

A complete, natural language with its own grammar, syntax, and vocabulary, expressed through hand shapes, facial expressions, and body movements, used primarily by Deaf communities in the United States and parts of Canada. ASL is not a signed version of English—it has distinct…

American Sign Language(also: ASL, Ameslan)

A complete, natural language that uses hand movements, facial expressions, and body posture to convey meaning, serving as the primary language of many Deaf people in the United States and parts of Canada. ASL has its own grammar and syntax distinct from English and is not a…

Americans with Disabilities Act(also: ADA, ADA 1990)

The Americans with Disabilities Act (ADA) is landmark US civil rights legislation enacted in 1990 that prohibits discrimination against individuals with disabilities in all areas of public life, including employment, education, transportation, and public accommodations. Title II…

Amnesia(also: Memory Loss, Amnestic Disorder)

A neurological condition characterised by the partial or complete inability to recall past experiences (retrograde amnesia) or to form new memories (anterograde amnesia). Amnesia results from damage to brain structures responsible for memory processing, commonly caused by…

Amyotrophic Lateral Sclerosis(also: ALS, Motor Neurone Disease, MND)

A progressive neurodegenerative disease that affects motor neurons controlling voluntary muscle movement, leading to progressive weakness, muscle wasting, and eventually loss of the ability to speak, swallow, and breathe. ALS is one of the primary conditions for which gaze-based…

Amyotrophic Lateral Sclerosis(also: ALS, Lou Gehrig's Disease, Motor Neurone Disease)

A progressive neurodegenerative disease affecting motor neurons in the brain and spinal cord, leading to muscle weakness, paralysis, and eventually respiratory failure. ALS typically progresses over 2-5 years, though some individuals live longer. For accessibility, ALS presents…

Anarthria

A severe motor speech disorder characterized by complete or near-complete loss of the ability to produce speech due to muscle weakness or paralysis affecting the articulatory organs (tongue, lips, palate, larynx). Unlike aphasia, which affects language processing, anarthria…

Anchor Text(also: Link Text, Hyperlink Text)

The visible, clickable text within a hypertext link that is intended to describe the link's destination or purpose. Descriptive anchor text (e.g., "download the annual report") provides clear information about what the user will find when they follow the link, while vague anchor…

Anchored Generative Model(also: Anchored Transformation Model)

A constrained AI generation approach where content creators define upper and lower bounds (anchors) of acceptable variation, and a generative model interpolates between these boundaries based on user preferences. In the context of caption customization, anchors are concrete…

Anchoring Effect(also: Anchoring Bias, Cognitive Anchoring)

A cognitive bias in which people rely too heavily on an initial piece of information (the "anchor") when making subsequent decisions or judgements. In the context of digital accessibility, the anchoring effect has been documented in alt text authoring, where content authors who…

Android Accessibility(also: Android A11y)

The accessibility features, APIs, and design guidelines built into the Android operating system that enable people with disabilities to use Android devices. Android accessibility includes TalkBack (screen reader), Switch Access, Voice Access, magnification, display adjustments,…

Android Accessibility Service(also: AccessibilityService, Android a11y Service)

The Android Accessibility Service is a system-level API that lets an app observe and interact with the UI of other applications on the device, exposing the hierarchical view tree (class names, text, bounds, clickability) and dispatching events such as focus changes, clicks, and…

Animal-Assisted Therapy(also: AAT, Pet Therapy)

A non-pharmacological therapeutic approach in which interaction with animals — typically dogs, cats, or horses — is used to support physical, cognitive, social, or emotional health goals. Evidence suggests AAT can reduce stress, lower blood pressure, and improve mood and…

Aniridia

A rare congenital eye condition involving the partial or complete absence of the iris, often accompanied by reduced visual acuity, light sensitivity (photophobia), nystagmus, and sometimes glaucoma or cataracts. Digital accommodations typically include high screen brightness…

Ankle Foot Orthosis(also: AFO, Ankle Brace, Foot Drop Brace)

An external medical device that encompasses the ankle joint and all or part of the foot, designed to support the ankle and improve gait in people with muscle weakness, spasticity, or structural deformity. AFOs are commonly prescribed for conditions such as cerebral palsy,…

Ankle-Foot Orthosis(also: AFO)

A lower-limb orthosis that supports the ankle and foot, typically prescribed to control foot drop, improve toe clearance during swing, and stabilise the ankle during stance. AFOs come in solid, hinged, posterior leaf-spring (PLS), and dynamic forms, made from thermoplastics,…

Annotation(also: Web Annotation, Content Annotation)

The practice of adding supplementary information, notes, or metadata to existing digital content, typically without modifying the original source. In accessibility, annotation is used to add alternative descriptions, labels, structural information, or other accessibility…

Annotation-based Transcoding(also: Annotation-driven Transcoding, External Annotation)

Annotation-based transcoding is a web accessibility technique in which a third party (not the site owner) authors a separate metadata file — the 'annotation' — that describes how to restructure or re-label a web page for screen reader users, and a transcoding proxy or browser…

Anomalous Trichromacy(also: Anomalous Trichromatic Vision)

A category of colour vision deficiency where all three types of cone cells are present but one type has a shifted sensitivity range, resulting in altered colour perception that is less severe than dichromacy. The three forms are protanomaly (shifted red cones), deuteranomaly…

Anomalous Trichromat(also: Anomalous Trichromacy, Colour Anomaly)

A person who has all three types of cone cells in the retina but one type has a shifted spectral sensitivity, causing altered colour perception that is less severe than dichromacy. Anomalous trichromats include protanomalous individuals (shifted L-cones, reduced red…

Anomia(also: Word-finding difficulty, Anomic aphasia)

Anomia is a language impairment characterized by difficulty retrieving words during speech, particularly the names of objects, people, or actions. It is the most common symptom across all types of aphasia and can also occur as a standalone condition (anomic aphasia). In…

Anonymization(also: Anonymity, Anonymous Communication)

The process of concealing a person's identity when they create or share content, enabling participation in discussions about sensitive, personal, or controversial topics without fear of identification or reprisal. While anonymization is straightforward for users of written…

Anterograde Amnesia

A form of amnesia in which a person is unable to form new memories following the onset of the condition, while memories from before the injury or illness may remain largely intact. Anterograde amnesia typically results from damage to the hippocampus or surrounding medial…

Anthropomorphism(also: Humanization, Anthropomorphization)

The attribution of human characteristics, emotions, intentions, or behaviors to non-human entities such as technology, animals, or objects. In assistive technology and conversational AI design, anthropomorphism raises important questions about how human-like an interface should…

Anticipatory Grasp(also: Pregrasp Planning, Pre-grasp, Pre-shaping)

Anticipatory grasp refers to the pre-shaping of the hand before contact with an object, based on expectations about the object's size, shape, and orientation. In sighted people this planning is driven primarily by visual input during the reach phase and produces smooth,…

Anticipatory Grief(also: pre-death grief, anticipatory mourning)

Grief experienced before an expected loss, particularly common among caregivers of individuals with progressive neurodegenerative conditions such as Alzheimer's disease. Anticipatory grief encompasses mourning not only of the anticipated death, but also of the ongoing losses…

Anxiety(also: Anxiety Disorder)

An emotional and physiological state characterised by apprehension about future threats, accompanied by heightened autonomic arousal (elevated heart rate, muscle tension, shallow breathing), attentional bias toward danger cues, and often avoidance behaviour. Clinical anxiety…

Aphantasia(also: Mind Blindness)

Aphantasia is a neurological condition in which a person is unable to voluntarily create mental images or visualize objects, people, or scenes in their mind. It affects an estimated 2-5% of the population and exists on a spectrum from reduced imagery to complete absence. In…

Aphasia

A language disorder that affects a person's ability to communicate, including difficulties with speaking, understanding speech, reading, and writing. Aphasia typically results from brain injury, most commonly stroke, and its severity and specific manifestations vary widely. In…

Aphasia Severity Rating(also: ASR Score, Aphasia Severity Rating Scale)

A clinician-administered ordinal scale, part of the Boston Diagnostic Aphasia Examination, indicating the severity of a person's aphasia on a 0-5 range where 0 indicates no usable speech or comprehension and 5 indicates minimal residual difficulties barely apparent to a…

Aphasia-Friendly(also: Aphasia-Accessible, Aphasia-Friendly Design)

A set of design practices for making written, spoken, and audiovisual content more accessible to people with aphasia. Established principles (Rose, Worrall, Hickson, Hoffmann) include short sentences with one idea per line, familiar everyday vocabulary, large sans-serif fonts…

App Review Mining(also: App Store Review Analysis, User Review Mining)

The process of systematically extracting, classifying, and analyzing user reviews from app stores such as Google Play and the Apple App Store to identify patterns, issues, and feature requests. In accessibility research, app review mining is used to discover real-world…

AppleVis

A community-driven website and discussion forum dedicated to accessibility on Apple platforms (macOS, iOS, iPadOS, tvOS, watchOS) for blind and low-vision users. It hosts app directories, podcasts, tutorials, and peer-support discussions focused on VoiceOver and related…

Application Profile(also: Metadata Application Profile)

A customization of an existing metadata standard that selects, constrains, or extends elements to meet the requirements of a particular community or application. In accessibility, application profiles are used to add accessibility-specific properties to general-purpose metadata…

Applied Behavior Analysis(also: ABA, ABA Therapy)

A therapeutic approach based on behavioral psychology principles that aims to increase desired behaviors and decrease undesired ones through systematic reinforcement. ABA is widely used as an intervention for autistic children, particularly in the United States. While proponents…

Applied Behavioral Analysis(also: ABA, Behavioral Analysis, Behaviour Analysis)

Applied Behavioral Analysis (ABA) is a scientific approach to understanding and changing behavior through systematic observation, measurement, and evidence-based intervention. In accessibility and disability contexts, ABA principles — including positive reinforcement, prompting,…

Applied Behavioural Analysis(also: ABA, Applied Behavior Analysis)

A therapeutic approach based on behaviorist principles that uses reinforcement and conditioning to modify behaviour, widely used with autistic children. ABA has become increasingly controversial within the autistic community and among disability scholars. Critics argue that it…

Applied behavior analysis(also: ABA, Behavior modification, Lovaas method)

A therapeutic approach based on the science of learning and behavior, widely used in interventions for children with autism spectrum disorder. ABA uses systematic reinforcement — rewarding desired behaviors with objects, food, praise, or other motivators — to teach new skills…

Appropriation

In HCI and accessibility research, the process by which users adapt, repurpose, or extend a technology beyond its designers' original intent to fit their own practices and contexts. Appropriation is often how disabled users bridge the gap between generic products and their…

Apraxia(also: Apraxia of Speech, Childhood Apraxia of Speech, CAS)

A motor speech disorder in which the brain has difficulty coordinating the muscle movements needed to produce speech, despite the muscles themselves not being weak. The person knows what they want to say but their brain has difficulty planning and sequencing the precise…