Glossary

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Abstract Widget(also: Abstract Interaction Object)

A user interface component defined by its semantic purpose and interaction behavior rather than its visual appearance. Abstract widgets specify what a user can do (select from options, enter text, trigger a command) without prescribing how the interaction is rendered — it could…

Accessibility Focus(also: A11y Focus, Screen Reader Focus)

The currently selected element in a user interface as perceived by a screen reader or other assistive technology. When an element has accessibility focus, the screen reader announces its description and the user can interact with it. Only one element can have accessibility focus…

Adaptive User Interface(also: AUI, Adaptive Interface, Self-Adapting Interface)

A user interface that automatically adjusts its presentation, behavior, or content based on user characteristics, preferences, context, or interaction patterns. Unlike customizable interfaces where users manually configure settings, adaptive interfaces use algorithms to detect…

Artboard(also: Canvas, Slide Canvas, 2-D Canvas)

An artboard is a two-dimensional digital workspace used in presentation software (PowerPoint, Google Slides, Keynote), graphic design tools, and whiteboard applications where objects like text boxes, shapes, images, and connectors can be placed at arbitrary positions. Artboards…

Assessment Descriptor(also: Visual Attribute Descriptor)

Brief visual attributes of objects — such as color, size, dimensions, and distance from the user — provided alongside obfuscated or spotlighted content to help users verify whether privacy techniques are working correctly. Research with blind participants has shown that common…

Audio Tone(also: Auditory Cue, Earcon)

Non-speech audio signals used to convey information such as the presence, location, or status of objects or interface elements. In accessibility contexts, audio tones can supplement or replace verbal descriptions, similar to how screen readers like JAWS use different sound…

Auditory User Interface(also: AUI, Audio User Interface)

A user interface that relies primarily on audio output — including synthesised speech, earcons, auditory icons, and sonification — to convey information and enable interaction. Auditory user interfaces are essential for users who are blind or have low vision, and they can…

Bi-Directional Alignment(also: Two-Way Alignment, Mutual Alignment)

An approach to human-AI interaction design that addresses alignment from both directions: not only adapting AI systems to match human values and preferences, but also helping humans understand, direct, and correct AI system behaviour. Traditional AI alignment focuses solely on…

Confidence Score(also: Confidence Rating, Certainty Score)

A numerical measure output by AI systems indicating how certain the system is about a particular result or classification. While confidence scores have been proposed as a way to help users assess AI accuracy, research with blind participants has found them difficult to interpret…

Cross-Representation Highlighting(also: Synchronized Highlighting, Linked Highlighting)

A user interface technique that synchronizes selections across multiple representations of the same data, so that selecting an element in one view automatically highlights the corresponding element in all other views. In accessible tools, cross-representation highlighting helps…

Dark Mode(also: Dark Theme, Night Mode)

A display setting that uses light-colored text and interface elements on a dark background, reversing the typical light-mode color scheme. Dark mode can benefit users with light sensitivity, photophobia, or certain visual conditions by reducing screen glare and brightness.…

Design System(also: Component Library, UI Kit)

A collection of reusable components, patterns, guidelines, and assets that together define the visual language and interaction standards for a product or organization. Design systems typically include UI components, typography, color palettes, icons, illustrations, and…

Digital Nudge(also: Technology Nudge, Behavioral Nudge)

Design elements in digital interfaces that subtly guide users toward particular behaviors or decisions. In privacy contexts, nudges might suggest obfuscating detected sensitive content or prompt users to review their sharing settings. HCI scholarship has critiqued nudging as…

Direct Manipulation(also: Direct Manipulation Interface, DMI)

An interaction style in human-computer interfaces where users directly act on visible objects rather than issuing commands. Key characteristics include continuous representation of objects, physical actions instead of complex syntax, and immediately visible results. Examples…

Dual User Interface(also: Dual Interface, Concurrent Accessible Interface)

An interface design approach in which two distinct, purpose-built user interfaces are provided simultaneously for different user groups — typically one visual interface for sighted users and one non-visual interface for blind or visually impaired users. Unlike screen reader…

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…

Floating Action Button(also: FAB)

A circular button that floats above the user interface in Android apps, typically representing the primary action on a screen. Defined by Google's Material Design guidelines, FABs usually display a simple icon (such as a plus sign, pencil, or heart) without visible text labels.…

Focusable Element(also: Keyboard Focusable, Focus Target)

A GUI element that can receive input focus, allowing users to interact with it via keyboard, switch device, or assistive technology. For screen reader users navigating mobile apps, an element without focus enabled is essentially invisible—they cannot select, activate, or even…

Freeze Frame(also: Video Thumbnail, ASL Freeze Frame)

In the context of ASL video interfaces, a freeze frame is a static image captured at a recognizable moment of an ASL sign, used as a visual label or thumbnail for video content. Freeze frames allow Deaf users to quickly scan, identify, and select content without watching full…

GUI Widget(also: UI Widget, User Interface Widget, Control)

A graphical user interface element that users can interact with or that displays information, such as buttons, text fields, images, checkboxes, and sliders. In mobile accessibility, widget types determine which accessibility requirements apply—interactive widgets like buttons…

Hapget(also: Haptically-Enhanced Widget)

A hapget (haptically-enhanced widget) is a user interface element that combines a 3D visual representation with haptic (touch) feedback, audio cues, and descriptive metadata to enable non-visual interaction. Introduced in the 3D HapticWebBrowser project, hapgets transform…

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 —…

Human Machine Interface(also: HMI, Human-Computer Interface)

The point of interaction between a human user and a machine, encompassing all hardware and software through which users control and receive feedback from a system. In accessible design, HMIs must support multiple modalities—visual, auditory, and haptic—to accommodate users with…

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

The physical or rendered dimensions of graphical interface elements such as icons, buttons, and interactive controls. Research consistently shows that larger icon sizes improve interaction performance for users with low vision and motor impairments. WCAG 2.1 Success Criterion…

Iconography(also: Icon Design, Icon System)

The design and systematic use of visual symbols to convey meaning in an interface. Good iconography balances recognisability, consistency, and cultural appropriateness so that users can interpret symbols quickly without reading text. For accessibility, icons alone are rarely…

Inter-Icon Spacing(also: Icon Spacing, Icon Gap)

The amount of empty space between icons or interactive targets in a graphical user interface. Inter-icon spacing affects a user's ability to visually distinguish, locate, and accurately select individual icons, particularly for people with visual impairments or motor…

Interaction Shell

A software component that renders user interface elements in a specific modality and handles direct interaction with the user. In the Fruit toolkit architecture, the interaction shell is separated from the application logic, allowing different shells (GUI, character-screen,…

Logical Metaphor(also: Spatial Metaphor)

A design technique for haptic feedback where the physical location of a vibration on the body is mapped to correspond with a spatial or conceptual dimension of the information being conveyed. For example, vibrations on the left, middle, and right positions of an armband can…

Loosely Coupled Interaction(also: Loosely Coupled Dual Interaction)

An interaction architecture in which two or more user interfaces share the same underlying content and data but operate independently through separate, non-overlapping input and output modalities. In a loosely coupled system, each interface is purpose-designed for its target…

Model-Based User Interface(also: MBUI, Model-Based UI)

An approach to user interface design where the interface is generated or adapted automatically from abstract models that describe the tasks users need to perform, the data domain, the user's characteristics, and the interaction context. Rather than hard-coding a single fixed…

Modifier Tactile Pattern(also: Modifier Tacton, Compound Tacton)

A vibrotactile design technique that combines two or more independent Tactons, each conveying a separate parameter, into a single composite pattern. Changing one component modifies one dimension of meaning while the other remains constant, allowing multiple pieces of information…

Multimodal Interface(also: Multimodal Interaction, Multi-Modal UI)

A multimodal interface is a system that communicates with users through multiple sensory channels simultaneously, such as speech, haptic feedback, sound, vibration, and visual output. In accessible navigation and assistive technology, multimodal interfaces are critical because…

Occlusion(also: Hand Occlusion, Finger Occlusion, Visual Occlusion)

In the context of touchscreen and pen-based interaction, occlusion refers to the user's hand or finger blocking their view of content on the screen while interacting with it. Occlusion is a significant accessibility barrier, particularly for older adults and users with motor…

On-Demand Simplification(also: On-demand text simplification, User-initiated simplification)

An interaction pattern for Automatic Text Simplification reading-assistance tools in which the user explicitly requests a simpler version of a word, phrase, or sentence — typically via hover, click, or tap — rather than having the system pre-apply simplifications to the page…

Picture-in-Picture(also: PiP, PIP)

A display technique that shows a smaller video or content window overlaid on the main content, allowing viewers to see two sources simultaneously. In accessibility contexts, picture-in-picture is the primary method for presenting sign language interpretation in video and…

Pluggable User Interface(also: Pluggable UI, Alternative User Interface)

A pluggable user interface is an interchangeable interface component that can be swapped in or out of an application without changing the application's core functionality. In the Universal Remote Console (URC) framework, pluggable user interfaces connect to an abstract "user…

Predictive Cursor(also: Anticipatory Cursor, Offset Cursor)

A cursor display technique designed to compensate for the delays inherent in speech-based or other high-latency input methods. A predictive cursor shows an indicator ahead of the actual cursor position, offset by the estimated distance the cursor will travel during the input…

Privacy Alert(also: Privacy Notification, Privacy Warning)

A notification informing users about the potential presence of private or sensitive content in their captured images or video. Privacy alerts aim to prompt users to apply obfuscation or take other protective action. However, research with blind users highlights tensions: while…

Semantic Hierarchy(also: Semantic Tree, Component Hierarchy)

A structured, tree-based representation of a complex object that organizes its components by meaning and relationship rather than by raw data. In accessible 3-D modeling, a semantic hierarchy breaks down a model into named, meaningful parts (e.g., "snowman body" containing…

Sign Language Interface(also: Sign-language interface, Signing interface)

A computing interface that accepts input from, or presents output to, a user in a signed language such as American Sign Language (ASL) or British Sign Language (BSL), rather than assuming a spoken or written language. Sign-language interfaces span sign-language recognition…

Speech Dialogue Design(also: Speech Interface Design, Auditory Dialogue Design)

The practice of designing the structure, content, ordering, and delivery of information presented through synthetic speech in computer interfaces. Effective speech dialogue design considers psycholinguistic principles such as the recency effect (items heard last are best…

Tacton(also: Tactile Icon, Vibrotactile Pattern)

A structured and abstract vibrotactile message designed to communicate complex information to users non-visually, analogous to how icons communicate information visually or earcons communicate through audio. Tactons encode information through vibration parameters such as rhythm,…

Tappability(also: Tap Target, Tappable)

The property of a user interface element that indicates whether it can be activated by tapping on a touchscreen device. Tappability is a key concern in mobile accessibility because elements that appear tappable but are not (or vice versa) create barriers for users who rely on…

Target Selection(also: Target Acquisition, Pointing)

The fundamental interaction task of moving a cursor or pointer to a specific location on screen and confirming selection, such as clicking a button or link. Target selection difficulty is affected by target size, distance to target, and user motor abilities—relationships…

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

The physical dimensions of an interactive element on screen — such as a link, button, or checkbox — that a user must point to and activate. Adequate target size is critical for users with motor impairments, tremor, or limited dexterity, as small targets require greater precision…

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…

UI Semantics(also: User Interface Semantics, Interface Semantics)

The meaningful properties and roles of user interface elements that go beyond their visual appearance, including what an element does, how it can be interacted with, and its relationship to other elements. UI semantics are essential for accessibility because assistive…

User Interface Management System(also: UIMS)

A software framework that separates user interface presentation and interaction from application logic, allowing the interface to be designed, modified, or replaced independently of the underlying program. A UIMS typically manages input handling, output rendering, and the…

Vibrotactile Feedback(also: VTF, Vibration Feedback)

A form of haptic feedback that communicates information through vibration patterns delivered to the skin, typically via small motors embedded in wearable devices such as armbands, gloves, or watches. Vibrotactile feedback offers an alternative sensory channel for conveying…

View Hierarchy(also: UI Hierarchy, Accessibility Hierarchy, DOM Tree)

The tree-structured representation of how user interface elements are organized and nested within an application. The view hierarchy defines parent-child relationships between UI components, specifying which elements are contained within others and how they are grouped. This…