Glossary

Search results

Dwell Time(also: Gaze Dwell, Fixation Duration)

The length of time a user must maintain their gaze on a target element to trigger a selection in eye gaze technology systems. Dwell time is a critical parameter in gaze-based interfaces: too short and users make unintended selections (the "Midas touch" problem), too long and…

Dwell-Based Selection(also: Dwell Selection, Dwell Time Selection)

An interaction technique used in eye-gaze and head-tracking interfaces in which holding the cursor over a target for a fixed duration (the 'dwell time', typically 300-1000 ms) triggers a selection, replacing the click action that a mouse user would perform. Dwell-based selection…

Dyadic Interaction(also: Dyad Interaction, Paired Interaction)

Social interaction between two individuals, studied as the fundamental unit of social exchange. In accessibility and intervention research, dyadic interaction is often examined in contexts such as child-caregiver pairs, student-peer partnerships, or client-therapist…

Dynamic Accessibility Analysis(also: Runtime Accessibility Testing, Dynamic A11y Analysis)

An approach to detecting accessibility issues by testing an application while it is running on a device or emulator, examining the actual rendered user interface rather than just the source code. Tools like Google's Accessibility Scanner perform dynamic analysis by evaluating…

Dynamic Bayesian Network(also: DBN, Temporal Bayesian Network)

A probabilistic graphical model that represents sequences of variables over time, extending standard Bayesian networks to handle temporal relationships. In accessibility and affective computing contexts, Dynamic Bayesian Networks are used to model how facial expressions, head…

Dynamic Caption Tracking(also: Word-by-Word Highlighting, Synchronized Caption Highlighting)

A caption display feature that highlights or visually emphasizes the word currently being spoken in the caption text, synchronized with the audio. Dynamic caption tracking helps viewers maintain their reading position within captions and re-engage after momentary attention…

Dynamic Content(also: Dynamic Web Content, Live Content)

Dynamic content refers to web page elements that change or update after the initial page load, either automatically (such as news tickers, stock prices, or chat messages) or in response to user interaction (such as search suggestions, form validation messages, or content loaded…

Dynamic Content Filtering(also: Intelligent Content Filtering, AI-Based Filtering)

The automated process of selectively showing or hiding web content based on computed relevance to a user's goals, preferences, or context. Dynamic content filtering uses AI models (such as large language models) to assess which page elements are relevant to a specific task and…

Dynamic Difficulty Adjustment(also: DDA, Adaptive Difficulty)

A system design approach that automatically or manually adjusts the precision, complexity, or challenge level of feedback and interaction based on the user's skill level and progress over time. Originally developed for video games to balance challenge and frustration, DDA has…

Dynamic Disability(also: Fluctuating Disability, Variable Disability)

A disability or impairment whose severity, manifestation, or impact varies over time — sometimes rapidly — rather than remaining constant. Dynamic disabilities are common in many health conditions such as cardiovascular disease, Parkinson's Disease, multiple sclerosis, and…

Dynamic HTML(also: DHTML)

A collection of technologies — including HTML, CSS, JavaScript, and the Document Object Model (DOM) — used together to create interactive and animated web content that can change after a page has loaded without requiring a server round-trip. Dynamic HTML was a precursor to…

Dynamic Keyboard(also: Adaptive Keyboard, Self-Adjusting Keyboard)

An assistive technology concept in which a keyboard automatically adjusts its input parameters — such as key repeat rate, debounce time, and acceptance delay — based on the user's typing patterns and abilities. Dynamic keyboards were developed to reduce common typing errors…

Dynamic Programming(also: DP, DP Matching)

A mathematical optimization technique used in pattern recognition that breaks complex problems into simpler overlapping subproblems. In accessibility technology, dynamic programming matching (DP matching) is commonly used in sign language recognition and speech recognition…

Dynamic Tactile Graphics(also: Interactive Tactile Graphics, Animated Tactile Graphics)

Tactile representations of visual information that can change, move, or respond to user interaction in real time, as opposed to traditional static tactile graphics which are fixed once produced. Dynamic tactile graphics can be created through shape displays with movable pins,…

Dynamic Time Warping(also: DTW)

An algorithm for measuring similarity between two temporal sequences that may vary in speed or timing. Dynamic time warping aligns sequences by warping the time axis to find the optimal match, making it robust to variations in how quickly gestures are performed. DTW is commonly…

Dynamic Type(also: Dynamic Text Size, Text Scaling, Font Scaling)

An iOS accessibility feature that allows users to adjust the system-wide text size to meet their reading needs, from very small to very large. Apps that support Dynamic Type automatically reflow and resize their text content when the user changes their preferred text size in…

Dysarthria(also: Motor speech disorder, Neuromotor speech impairment)

A group of speech disorders caused by weakness, paralysis, or lack of coordination in the muscles used for speaking, resulting from damage to the brain or nervous system. Speech may sound slurred, slow, or difficult to understand, though the person's language comprehension and…

Dysarthric Speech(also: Dysarthria)

Dysarthric speech is speech that is affected by dysarthria, a motor speech disorder resulting from neurological injury or conditions that affect the muscles used for speech production. Characteristics include imprecise articulation, irregular speech rate, abnormal pitch and…

Dysautonomia

A group of conditions caused by dysfunction of the autonomic nervous system, which controls involuntary functions like heart rate, blood pressure, digestion, and temperature regulation. Dysautonomia can cause fatigue, dizziness, fainting, and cognitive difficulties that impact…

Dyscalculia(also: Math Learning Disability, Number Blindness, Mathematics Disorder)

A specific learning disorder that affects the ability to acquire, understand, and manipulate numerical and mathematical concepts. People with dyscalculia may have difficulty with number sense, memorizing arithmetic facts, performing calculations, and understanding mathematical…

Dysfluency(also: Disfluency, Speech Dysfluency)

An interruption in the normal flow of speech, including repetitions of sounds, syllables, or words ("b-b-because"), prolongations of sounds ("ssssnake"), blocks (silent pauses where speech is temporarily stopped), and interjections ("um", "uh"). While occasional dysfluencies are…

Dysgraphia(also: Disorder of written expression, Specific learning disorder in written expression)

A neurological learning disability that affects written expression, including handwriting legibility, spelling accuracy, and the ability to organize thoughts in writing. Dysgraphia can make text entry and written composition cognitively exhausting, creating significant barriers…

Dyskinesia(also: Levodopa-Induced Dyskinesia, LID)

A movement disorder characterized by involuntary, uncontrollable movements such as twitching, swaying, or jerking, most commonly associated with long-term use of levodopa medication for Parkinson's disease. Dyskinesia can significantly affect a person's ability to use standard…

Dyslexia

A specific learning disability that primarily affects reading, writing, and spelling skills. Dyslexia is neurological in origin and is characterized by difficulties with accurate or fluent word recognition, poor spelling, and decoding abilities. It is not related to…

Dyslexia(also: Reading Disability, Developmental Dyslexia)

A neurologically-based learning disability that primarily affects the acquisition and processing of written language, manifesting as difficulties with reading, writing, spelling, and phonological processing. Dyslexia varies in severity and is estimated to affect 10-17% of the…

Dyslexia Screening(also: Dyslexia Assessment, Reading Disability Screening)

The process of identifying individuals who may be at risk for dyslexia, typically through standardized tests that assess reading fluency, phonological awareness, rapid naming, and other cognitive indicators associated with the condition. Traditional screening requires trained…

Dysphagia(also: Swallowing Disorder, Swallowing Difficulty)

A swallowing disorder that makes it difficult or impossible to move food or liquid from the mouth to the stomach safely. Dysphagia commonly occurs alongside communication disorders following stroke, traumatic brain injury, or neurological conditions. While not directly a…

Dysphonia(also: voice disorder, phonation disorder)

A voice disorder characterized by abnormal pitch, loudness, quality, or resonance of the voice resulting from impaired function of the larynx or vocal cords. Dysphonia can range from mild hoarseness to complete voice loss (aphonia) and may be caused by vocal cord nodules,…

Dyspnea(also: Breathlessness, Shortness of Breath)

A subjective experience of breathing discomfort consisting of qualitatively distinct sensations that vary in intensity, as defined by the American Thoracic Society. People who experience dyspnea commonly describe sensations of respiratory effort, chest tightness, and air hunger.…

Dyspraxia(also: Developmental Coordination Disorder, DCD)

A neurodevelopmental condition affecting motor planning, coordination, and the sequencing of movements. People with dyspraxia have difficulty translating intended actions into coordinated physical movements, despite having adequate muscle strength and understanding of what they…

Dysregulation(also: Emotional Dysregulation, Sensory Dysregulation)

Dysregulation is a state in which a person's emotional, sensory, or physiological response exceeds what they can manage given the current context - typically manifesting as distress, overwhelm, shutdown, or outburst. It is common in autism, ADHD, noise sensitivity, PTSD, and a…

Dystonia(also: Dystonic Movements)

A movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive movements, postures, or both. Dystonia can affect a single body part (focal dystonia), adjacent regions (segmental), or the whole body (generalized). In…

E-Book Accessibility(also: Electronic Book Accessibility, Digital Book Accessibility)

The design and implementation of electronic books to be usable by people with disabilities, including proper semantic structure, text resizing, reflowable content, alternative text for images, compatibility with screen readers, and customizable visual presentation. Despite the…

E-Commerce Accessibility(also: Accessible E-Commerce, Online Shopping Accessibility)

The degree to which online shopping experiences — product discovery, evaluation, checkout, fulfilment, customer support, and (on peer-to-peer platforms) selling — are usable by people with disabilities, particularly blind and low-vision (BLV) users who depend on screen readers,…

E-Government Accessibility(also: Digital Government Accessibility, E-Gov Accessibility)

The practice of ensuring that electronic government services — including websites, online forms, and digital public services — are usable by people with disabilities. E-government accessibility is particularly important because government services are often essential and…

E-Health(also: eHealth, Electronic Health)

The use of information and communication technologies for health services, including electronic health records, telemedicine, mobile health applications, and patient portals. E-health aims to improve healthcare access, efficiency, and quality, but accessibility barriers in…

E-Ink Display(also: Electronic Ink, E-Paper, Electronic Paper Display)

A display technology that mimics the appearance of ink on paper by using electrically charged particles to create images. E-ink displays are characterized by high readability in direct light, minimal glare, extremely low power consumption, and reduced eye strain compared to…

E-Learning(also: Electronic Learning, eLearning, Online Learning)

Education and training delivered through digital technologies, primarily via the internet and computer-based platforms. E-learning encompasses a range of approaches from fully online courses to supplementary digital materials, enabling learners to access content at their own…

E-Recruiting(also: Electronic Recruiting, Online Recruiting, Digital Recruitment)

The use of web-based tools and platforms for job posting, candidate sourcing, application submission, and hiring management. E-recruiting systems include job search websites, online application portals, applicant tracking systems, and social networking platforms like LinkedIn.…

E-Tran Frame(also: Eye-Transfer Frame, Eye-Pointing Frame, ETRAN)

A low-technology augmentative and alternative communication (AAC) device consisting of a transparent frame or board that allows a person to communicate by directing their eye gaze toward symbols, letters, words, or colour-coded groups arranged on the frame. The communication…

E-learning accessibility(also: Online learning accessibility, Accessible e-learning)

The design and delivery of online educational content and platforms so that learners with disabilities can participate equally. This includes accessible learning management systems, video lectures with captions and descriptions, navigable course materials, and interactive…

E-textiles(also: Electronic Textiles, Smart Textiles)

E-textiles are textile objects that integrate electronic components such as sensors, lights, or actuators into their design. They combine traditional textile techniques (sewing, embroidery, weaving) with electronic circuitry, often using conductive yarn or thread to create…

EARL(also: Evaluation and Report Language)

A machine-readable format developed by the W3C for expressing the results of accessibility evaluations in a standardized way. EARL uses RDF (Resource Description Framework) to describe test results including the outcome (pass, fail, cannot tell, inapplicable, untested), the test…

ELAN(also: EUDICO Linguistic Annotator)

A free, open-source annotation tool developed at the Max Planck Institute for Psycholinguistics for creating, editing, and searching multi-tier, time-aligned annotations on video and audio recordings. ELAN has become the de-facto standard tool for sign-language corpus work…

EMG Switch(also: Electromyography Switch, Muscle Signal Switch)

An assistive technology switch that detects electrical signals produced by muscle contractions (electromyography) to generate a switch activation. EMG switches can detect even very small muscle movements, such as a slight facial twitch or jaw clench, making them suitable for…

EN 301 549(also: European accessibility standard)

The European standard for accessibility requirements of ICT products and services, harmonized under the European Accessibility Act. EN 301 549 covers web content, software, hardware, and documentation, incorporating WCAG 2.1 Level AA for web and non-web documents while adding…

EPUB(also: EPUB 3, Electronic Publication)

An open standard file format for digital books and publications maintained by the World Wide Web Consortium (W3C), formerly by the International Digital Publishing Forum (IDPF). EPUB 3, the current major version, is based on HTML5, CSS, and JavaScript, which means web…

ESP Game(also: Extra Sensory Perception Game)

A human computation game, created by Luis von Ahn, in which two randomly paired online players are shown the same image and independently type words to describe it, earning points when their labels match. The ESP Game was designed to generate accurate, human-validated labels for…

EU AI Act(also: European Union Artificial Intelligence Act, Artificial Intelligence Act (EU))

A European Union regulation, adopted in 2024, that establishes a risk-based framework for AI systems deployed in the EU. High-risk systems — including AI used in employment, hiring, worker management, education, and access to essential services — are subject to obligations…

EVITA(also: Enabling Visually Impaired Table Access)

A specialized table browser developed at the University of Manchester designed to enable visually impaired users to navigate, browse, and read HTML data tables non-visually in a manner analogous to how sighted readers interact with tables in print. EVITA provides keyboard-based…