Glossary

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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 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-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 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…

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…

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…

Transcoding(also: Content transcoding, Web transcoding)

The process of converting or transforming web content from one format or structural representation to another to improve accessibility. In the context of screen reader access, transcoding can involve detecting visual layout semantics like grid structures and converting them into…

Transcription(also: Speech-to-Text Transcription, Real-Time Transcription)

The process of converting spoken language into written text, either in real time or after the fact. In accessibility contexts, transcription services provide communication access for deaf and hard of hearing individuals by producing text versions of spoken content in classrooms,…

Transfer Function(also: Mapping Function, Control-Display Gain)

A mathematical function that defines the relationship between an input signal and an output response in a control system. In assistive technology and pointer control, a transfer function determines how physical movements (such as head movements, eye gaze, or joystick input) are…

Transformation Proxy(also: Transcoding Proxy, Web Accessibility Proxy)

A transformation proxy is an intermediary server that sits between a user and the web, intercepting web pages and modifying their content before delivering them to the user's browser. In accessibility contexts, transformation proxies are used to improve the accessibility of web…

Transparent Video Overlay(also: Transparent Video, Video Overlay, Translucent Video)

A display technique where a live video feed is rendered as a semi-transparent layer on top of another application, allowing users to see both the video content and the underlying application simultaneously. In accessibility contexts, transparent video overlays have been used to…

Trimodal Feedback(also: Triple-Modality Feedback)

A form of interface feedback that delivers information through three simultaneous sensory channels — typically auditory, haptic, and visual. Trimodal feedback offers the highest level of redundancy in multimodal interface design, ensuring that users can perceive system responses…

Turn-by-turn navigation(also: Step-by-step navigation, Guided navigation)

A navigation method that provides sequential walk-and-turn instructions to guide a user along a route without requiring prior knowledge of the environment. For people with visual impairments, turn-by-turn systems typically use audio cues or speech instructions to indicate when…

Tutoring System(also: Intelligent Tutoring System, ITS, Computer-Based Tutor)

Software that provides personalised instruction and feedback to learners, adapting its responses based on the learner's performance, knowledge level, and error patterns. In accessibility contexts, tutoring systems can be designed to support learners with disabilities by…

Two-Point Discrimination(also: Spatial Acuity, Tactile Acuity)

A measure of tactile sensitivity indicating the minimum distance at which two distinct points of contact on the skin can be perceived as separate rather than as a single point. Lower values indicate higher sensitivity. The fingertips have the highest two-point discrimination…

UAAG(also: User Agent Accessibility Guidelines)

A set of guidelines from the W3C Web Accessibility Initiative that explains how to make user agents — browsers, media players, and other applications that render web content — accessible to people with disabilities. UAAG addresses how user agents should support assistive…

UI Agent(also: User Interface Agent, Browser Agent, AI Agent)

An AI-powered software system that can autonomously interact with graphical user interfaces on behalf of a user, performing tasks by interpreting natural language commands and translating them into interface actions such as clicking buttons, entering text, and navigating between…

Ubiquitous Accessibility(also: Accessibility Everywhere)

A vision for accessibility in which individuals can invoke their needed assistive technologies or access features on any computing device they encounter, rather than being limited to personally owned and configured equipment. As computing becomes embedded in public spaces,…

Ultra-Wideband(also: UWB, Ultra wideband)

A short-range radio-frequency technology that uses very wide frequency bands (typically above 500 MHz) and very short pulses to enable centimetre-accurate distance and angle-of-arrival measurements between paired devices. UWB is increasingly used in accessibility for indoor…

Ultrasonic Sensor(also: Ultrasound Sensor, Proximity Sensor)

A device that measures distance to objects by emitting high-frequency sound waves and calculating the time it takes for the echo to return. In assistive technology, ultrasonic sensors are commonly used in electronic travel aids and wearable navigation devices for blind and…

Unaided AAC(also: Unaided Augmentative and Alternative Communication, Body-Based AAC)

The branch of Augmentative and Alternative Communication that relies solely on the user's body — gestures, facial expressions, vocalisations, manual signs, body orientation — without an external device. Unaided AAC is fast, always available, and naturally expressive; families,…

Unimodal Interface(also: Single-Mode Interface)

An interface that accepts input through only one mode or channel of interaction, such as keyboard-only, voice-only, or gesture-only input. In contrast to multimodal interfaces that combine multiple input methods, unimodal interfaces rely on a single input modality for command…

Unistroke Gesture(also: Single-Stroke Gesture, Unistroke)

A unistroke gesture is a shape or symbol drawn in a single continuous stroke on a touch screen or digitizer, which is then recognized by software as a specific command or input. In accessible interfaces for blind users, unistroke gestures provide an efficient way to create…

Unit Selection Synthesis(also: Concatenative Unit Selection, Unit Selection TTS)

A text-to-speech synthesis approach that generates speech by selecting and concatenating variable-length segments of pre-recorded human speech from a large database to match the input text. Unit selection synthesizers generally produce more natural-sounding speech than…

Universal Maths Conversion Library(also: UMCL)

An open-source programming library that encapsulates converters for different Braille mathematical codes, enabling applications to convert between MathML and various national Braille mathematical notations. UMCL supports multiple Braille math systems including Nemeth code (used…

Universal Remote Console(also: URC, URC Framework)

The Universal Remote Console (URC) is an ISO/IEC standard framework (ISO/IEC 24752) that enables pluggable, alternative user interfaces for applications and devices. URC separates the user interface from the underlying application through an abstract "user interface socket" that…

Universe of One(also: Universe-of-One, Personalized Prompting)

A design approach in assistive technology where content, prompts, and guidance are tailored to each individual user rather than providing generic or standardized instructions. The concept is particularly important for people with cognitive impairments, who often struggle with…

Unobtrusive Interaction(also: Unobtrusive Interfaces)

A design orientation, associated with ambient, wearable, and assistive-technology research, that aims to minimise disruption to users' natural behaviour, attention, and social presence. Rather than demanding foreground engagement (pulling up a phone, pressing through menus,…

Upper-Limb Prosthetic(also: Upper Limb Prosthesis, Arm Prosthetic, Hand Prosthetic)

A prosthetic device that replaces or augments part or all of a missing upper limb — fingers, hand, wrist, forearm, or full arm. Upper-limb prosthetics range from passive cosmetic devices and body-powered cable-driven hands to externally powered myoelectric systems that read…

User Agent(also: Browser, Web Browser)

In web accessibility, a user agent is any software that retrieves, renders, and facilitates user interaction with web content. This includes mainstream web browsers like Chrome, Firefox, and Safari, as well as assistive technologies such as screen readers that work alongside…

User Interface Agent(also: Interface Agent, Software Agent, Assistant Agent)

A software component that observes user behaviour and the state of an application, then unobtrusively offers help — suggestions, shortcuts, summaries, or warnings — to reduce workload or prevent errors. In accessibility research, interface agents have been used to monitor a…

User model(also: User modeling, User modelling)

A computational representation of a user's characteristics, abilities, preferences, and behavior patterns, used to predict how they will interact with a system or to adapt an interface to their needs. In accessibility contexts, user models capture attributes such as motor range…

User profile(also: User model, Personal needs and preferences profile, PNP)

A structured collection of data describing a user's characteristics, capabilities, preferences, and requirements for interacting with a computing system. In accessibility, user profiles inform how interfaces should adapt to meet individual needs. Traditional approaches (such as…

Utterance-Based System(also: Utterance-Based AAC, Prestored Message System)

A type of augmentative and alternative communication (AAC) system that uses prestored phrases, sentences, or complete utterances rather than requiring users to construct messages word-by-word or letter-by-letter. Utterance-based systems organise prestored text hierarchically,…

VBraille(also: V-Braille, Vibration Braille)

A method for representing Braille characters on a smartphone touchscreen using vibration feedback. The screen is divided into a 3-row by 2-column grid matching a standard Braille cell layout, and the phone vibrates when the user touches regions corresponding to raised dots in…

VQA(also: Visual Question Answering)

VQA (Visual Question Answering) is an AI task in which a system answers natural-language questions about the content of an image. In assistive contexts, VQA systems such as Be My AI, Seeing AI, and Aira let blind and low-vision users ask about their visual surroundings - from…

VR Accessibility Training(also: Virtual Reality Training for Accessibility, VR-Based AT Training)

The use of virtual reality environments to teach people with disabilities how to use assistive technologies or navigate unfamiliar real-world scenarios in a safe, controlled setting. VR training allows users to practice spatial and physical skills — such as aiming a smartphone…

Variable Friction(also: Variable Friction Display, Friction Modulation)

A surface haptics technique that dynamically adjusts the friction between a user's fingertip and a touchscreen surface to create the sensation of different textures. Typically achieved through ultrasonic vibration that creates a thin cushion of air beneath the fingertip,…

Variable Pointing Performance(also: Variable Pointing Ability, Intermittent Pointing Difficulty)

A condition where a person's ability to accurately use a pointing device (such as a mouse, trackpad, or touchscreen) fluctuates over time due to factors like physical impairments, fatigue, medication effects, aging, or environmental conditions. Unlike permanent severe motor…

Verbosity(also: Verbosity Level, Screen Reader Verbosity)

Verbosity refers to the level of detail that an assistive technology — particularly a screen reader or voice browser — provides when announcing interface elements and content. Most screen readers allow users to adjust verbosity settings to control how much contextual information…

Verbosity Level(also: Verbosity Setting, Detail Level)

A configurable setting that controls the amount of detail provided in text or audio descriptions of content, particularly for screen reader users and accessible data visualizations. Verbosity levels typically range from low (minimal summary with key points only) to high…

Verbosity Settings(also: Screen Reader Verbosity, Announcement Settings)

Configuration options that control the amount of detail a screen reader or accessible application announces to the user. Verbosity settings allow users to adjust the balance between receiving comprehensive information and reducing auditory noise. In development environments,…

Verification loop(also: Feedback loop, Edit-verify cycle)

An interaction pattern in which a user performs an action, receives feedback about the result, evaluates whether the outcome matches their intent, and decides whether to accept, undo, or refine the action. In non-visual accessibility contexts, verification loops are essential…

Vibration Feedback(also: Haptic vibration, Vibrotactile feedback)

The use of controlled vibration patterns — varying in duration, interval, intensity, and spatial location — to convey information to a user through the sense of touch. In assistive technology for blind people, vibration feedback has two advantages over audio feedback: it does…