Glossary

Search results

Time-Based Media(also: Multimedia Content, Synchronized Media)

Content that unfolds over time, including audio, video, audio-video combinations, and interactive multimedia presentations. WCAG Guideline 1.2 requires that time-based media be made accessible through alternatives such as captions for the deaf and hard of hearing, audio…

Time-Causal Model(also: Temporal Causal Model, Sequential Logic Model)

A computational model that enforces temporal coherence in predictions by ensuring that the sequence of recognized events follows a logical causal order. In recipe tracking, a time-causal model prevents the system from predicting that an earlier step is currently happening after…

Time-Lapse Photography

A photographic technique that captures a series of still images at set intervals over a period of time. In accessibility contexts, time-lapse photography has been explored as an alternative to video capture for making visual content available to people with visual disabilities.…

Time-compressed Speech(also: Accelerated Speech, Speed-altered Speech)

Speech that has been digitally processed to play at a faster rate than it was originally recorded or synthesized, while preserving pitch. Unlike simply increasing playback speed (which raises pitch), time compression algorithms remove small portions of the audio signal to reduce…

Time-of-Flight Camera(also: TOF Camera, ToF Sensor, Depth Camera)

A type of camera sensor that measures the distance to objects by calculating the time it takes for emitted light (typically infrared) to travel to a surface and reflect back. Time-of-Flight cameras produce 3D depth maps of their environment in real time, making them useful in…

Timed Text(also: Timed Text Markup Language, TTML, DFXP)

Timed Text Markup Language (TTML) is a W3C standard for representing timed text content such as captions, subtitles, and other text synchronized with audio or video media. Originally developed as the Distribution Format Exchange Profile (DFXP), TTML provides an XML-based format…

Tinnitus(also: Ringing in the Ears)

Tinnitus is the perception of sound - most commonly ringing, buzzing, or hissing - without a corresponding external source. It can be continuous or intermittent, uni- or bilateral, and ranges from mild background nuisance to severely disabling. Tinnitus is often associated with…

Tiresias(also: Tiresias Screenfont, Tiresias Font Family)

A family of typefaces developed in 1998 by the Royal National Institute of Blind People (RNIB) specifically designed for legibility on screen displays, particularly television subtitling. Named after the blind prophet of Greek mythology, Tiresias became one of the most widely…

Tokenism(also: Token Inclusion)

The practice of including a small number of individuals from underrepresented groups primarily for the appearance of inclusivity rather than for meaningful participation or impact. In accessibility research, tokenism occurs when studies include a minimal number of disabled…

Tonal Language(also: Tone Language)

A language in which pitch variations at the word or syllable level distinguish meaning, so that the same sequence of consonants and vowels can have entirely different meanings depending on the tone used. Languages like Mandarin Chinese, Thai, and Vietnamese are fully tonal,…

Tone indicator(also: Tone tag)

A text-based marker appended to online messages to explicitly signal the intended emotional tone or communicative intent, such as /s for sarcasm, /j for joking, /gen for genuine, or /srs for serious. Tone indicators emerged from neurodivergent online communities to address the…

Tongue Display Unit(also: TDU, BrainPort, Tongue Electrotactile Display)

A sensory substitution device that presents visual or spatial information through an array of electrodes placed on the tongue. The tongue is ideal for electrotactile stimulation because it has a very high density of nerve endings, low and consistent electrical impedance due to…

Tool Substitution(also: Adaptive Tool Use, Alternative Tool Use)

The practice of using a different tool than what is specified or expected to accomplish a task, common among people with disabilities who adapt their approaches based on available resources, physical capabilities, or personal preference. In non-visual cooking, BLV individuals…

Tooltip(also: Form Field Tooltip, Accessible Name (PDF))

In PDF forms, a tooltip is the programmatic label associated with a form field that assistive technologies read aloud when the user reaches that field. Unlike HTML, PDF does not have a native label-to-field association, so the tooltip carries the accessible name. Best practice…

Topic Modeling(also: LDA, Latent Dirichlet Allocation)

A machine learning technique that automatically discovers abstract themes or topics within a collection of documents by analyzing patterns of word co-occurrence. Latent Dirichlet Allocation (LDA) is the most widely used topic modeling algorithm. In accessibility research, topic…

Topic Segmentation(also: Text Segmentation, Topicalisation)

A natural language processing technique that automatically divides a document into coherent sections based on changes in topic or subject matter. Topic segmentation algorithms detect boundaries where the semantic content of adjacent sentences or paragraphs shifts significantly,…

Topicalization(also: Topic-Comment Structure)

A grammatical construction common in American Sign Language and other sign languages in which the topic of a sentence is placed first and marked by non-manual signals — typically raised eyebrows, a head tilt, and a brief pause — followed by a comment about that topic. For…

Total Communication

An approach to communication that incorporates all available modes and channels—including speech, gesture, facial expression, drawing, writing, pointing, props, and physical aids—rather than relying on a single modality. Total communication is particularly relevant for people…

Touch Accessibility(also: Touchscreen Accessibility)

The design and adaptation of touch-based interfaces to be usable by people with diverse motor, sensory, and cognitive abilities. Touch accessibility addresses challenges including insufficient target sizes for users with limited fine motor control, lack of alternatives to…

Touch Drift(also: Finger Drift)

The displacement of a finger's contact point on a touchscreen between the initial finger-down position and the final finger-up position during a single touch interaction. Touch drift measures how far a touch "slides" from where it started to where it ended, distinct from touch…

Touch Exploration(also: Explore by Touch, Touch-Based Exploration)

An interaction method that allows users to discover on-screen content by moving their finger across a touchscreen, receiving audio feedback about elements under the fingertip. Touch exploration is fundamental to how blind and low-vision users navigate mobile devices through…

Touch Panel(also: Touch Tablet, Touch-Sensitive Panel, Digitizer Tablet)

A flat, pressure-sensitive input surface that detects the position of a finger or stylus when it makes contact. Unlike touchscreens, which combine display and input on the same surface, a touch panel is a separate input device placed over or alongside a display. In…

Touch Reader(also: Tactile Reader, Tactile Graphics Reader)

A person who reads and interprets information through touch, particularly tactile graphics, raised line drawings, and braille. Touch readers include blind and low-vision individuals who access spatial and graphical information through tactile media rather than vision. The skill…

Touch Screen Accessibility(also: Touchscreen Accessibility, Touch Input Accessibility)

The design and implementation of touch-based interfaces so they can be effectively used by people with various disabilities, including those with motor impairments, low vision, or blindness. Touch screen accessibility challenges include the requirement for precise finger…

Touch Sensor(also: Touch-Sensitive Sensor, Tactile Sensor)

An electronic component that detects physical contact or proximity of a finger or object on a surface. Touch sensors are used in accessible devices to enable direct tactile interaction, allowing blind users to trigger audio feedback by touching specific locations on a physical…

Touch Target(also: Tap Target, Hit Area, Target Size)

A touch target is the area on a touchscreen interface that responds to a user's tap or touch input. Accessibility guidelines recommend minimum touch target sizes to ensure that people with motor impairments, limited dexterity, or larger fingers can reliably activate interactive…

Touch Target Size(also: Tap Target Size, Target Size)

The physical area of an interactive element on a touchscreen that responds to user input. Adequate touch target sizing is critical for accessibility, particularly for users with motor impairments who may have difficulty precisely tapping small areas. WCAG 2.2 Success Criterion…

Touch target(also: Tap target, Touch target size, Target size)

The interactive area on a touchscreen or pen-based display that responds to user input when tapped or pressed. Touch target size is a critical accessibility consideration because targets that are too small or too closely spaced cause selection errors, particularly for older…

Touch-Free Interaction(also: Contactless Interaction, No-Touch Interface)

Interaction with digital systems without physically touching any device surface, achieved through gestures, voice, eye tracking, brain-computer interfaces, or proximity sensors. Touch-free interaction is important for accessibility because touchscreens present significant…

Touch-to-Explore(also: Touch Exploration, Explore by Touch)

An interaction mode used by touchscreen screen readers (such as VoiceOver on iOS and TalkBack on Android) where users drag their finger across the screen to discover and hear descriptions of interface elements beneath their fingertip. As the user's finger passes over buttons,…

Touchpad(also: Touch Tablet, Touch-Sensitive Pad)

A flat, pressure-sensitive input device that detects the position of a finger or stylus on its surface. In assistive technology contexts, touchpads are used as interactive overlays for tactile graphics and maps, enabling users who are blind to place a tactile printout on the pad…

Touchpad Navigation(also: Trackpad Navigation)

A method of interacting with digital content by dragging fingers or pressing specific positions on a smooth-surface touchpad input device. In accessibility contexts, touchpad navigation enables direct manipulation of spatial interfaces — such as maps or diagrams — by mapping…

Touchscreen(also: Touch Screen, Touch Display)

An input and display device that detects touch gestures directly on its surface, allowing users to interact with content by tapping, swiping, pinching, or dragging. While touchscreens enable intuitive direct manipulation, they present accessibility challenges for users with…

Touchscreen Accessibility(also: Touch Interface Accessibility)

Touchscreen accessibility refers to the design principles, techniques, and assistive technologies that make touchscreen devices usable by people with disabilities. This includes screen reader gestures (such as VoiceOver on iOS and TalkBack on Android), which allow blind users to…

Touchscreen Exploration(also: Touch Exploration, Direct Touch Exploration)

An accessibility interaction mode where blind and low vision users explore digital content by moving their finger across a touchscreen, receiving audio or haptic feedback about elements beneath their fingertip. Touchscreen exploration has been applied to 2-D interfaces (through…

Touchscreen text entry(also: Mobile typing, Virtual keyboard input)

The process of entering text on a touchscreen device using a virtual keyboard, which presents significant accessibility challenges for blind and visually impaired users who cannot see key boundaries or visual feedback. Screen reader users typically employ an explore-then-lift…

Tower of Hanoi(also: Tower of Hanoi Task, Tower Task)

The Tower of Hanoi is a classic cognitive assessment puzzle used in neuropsychology and educational research to measure multi-step planning and executive function abilities. The task requires moving a set of discs or objects from one position to another according to specific…

Toxic positivity(also: Forced positivity, Positive bypassing)

Toxic positivity refers to the excessive promotion of optimistic or uplifting framing that dismisses, minimises, or erases negative emotions, suffering, and genuine hardship. In disability contexts, toxic positivity manifests when portrayals of disabled people focus exclusively…

Toxicity detection(also: Content toxicity scoring, Toxic speech detection)

An NLP-based content moderation technique that assigns scores to text indicating the likelihood it is rude, disrespectful, or likely to make someone leave a conversation. Research has shown that toxicity detection models encode disability bias, scoring innocuous sentences that…

Trace Center(also: Trace Research and Development Center)

A leading accessibility research center originally founded at the University of Wisconsin-Madison in 1971, now at the University of Maryland. The Trace Center pioneered foundational work in accessible technology, including early accessibility guidelines that influenced Section…

Trace R&D Center(also: Trace Center, Trace Research and Development Center)

A pioneering research center focused on accessibility and assistive technology, originally established at the University of Wisconsin-Madison in 1971 and later affiliated with the University of Maryland. Founded and long directed by Gregg Vanderheiden, the Trace Center developed…

Tracheoesophageal puncture(also: TEP, tracheoesophageal voice prosthesis, TE puncture)

A surgical procedure that creates a small opening (fistula) between the trachea and esophagus to restore voice production after total laryngectomy. A one-way valve is inserted that allows exhaled air to pass into the esophagus, where vibrations in the pharyngoesophageal segment…

Tracheostomy(also: Tracheotomy)

A surgical procedure that creates an opening (stoma) in the front of the neck into the trachea (windpipe), through which a tube is inserted to provide an airway for breathing. Like intubation, a tracheostomy typically prevents or significantly impairs speech because air no…

Trackball

A trackball is a pointing device consisting of a ball housed in a stationary socket that the user rotates to move the on-screen cursor, with buttons nearby for clicking. Unlike a mouse, a trackball does not require arm movement across a surface, making it valuable for people…

Tracked Captions(also: Speaker-following captions, Dynamic captions)

Captions that move dynamically within the video frame to stay near the current speaker's face or mouth, rather than remaining anchored at a fixed position (typically the bottom of the video). Tracked captions reduce the visual effort required for Deaf and Hard-of-Hearing viewers…

Training Data(also: Training Set, Training Dataset)

The collection of labeled examples used to teach a machine learning model to perform a specific task. The quality, quantity, and diversity of training data directly determine how well a model will perform. In accessibility contexts, training data quality is especially important…

Training Wheels Interface(also: Training Wheels, Progressive Disclosure)

An interface design pattern that reduces complexity for novice users by hiding or disabling advanced features until they are needed, then gradually revealing them as the user gains competence. Named after the stabilizing wheels on children's bicycles, this approach prevents…

Trajectory Analysis(also: Route Analysis, Path Analysis)

The computational study of movement patterns over time and space, typically derived from GPS or other location data. Trajectory analysis involves modelling, comparing, and classifying sequences of spatial positions to identify patterns, anomalies, or behaviours. In assistive…

Trajectory Playback(also: Haptic Playback, Force-Guided Movement)

A technique in haptic interfaces where a force-feedback device physically guides a user's hand through a predefined path or shape. The system applies forces to move the user along a trajectory, allowing them to perceive spatial information through proprioception and kinesthetic…

Transactional Communication Model

The most dynamic model of communication, in which all parties are simultaneously senders and receivers, co-creating meaning through instantaneous, continuous feedback. In this model, communication is a collaborative process where context, environment, and shared understanding…