Glossary

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Accelerated Speech(also: Time-Compressed Speech, Speed-Up Speech)

Audio output played at faster than normal speaking rate, commonly used by people with visual impairments when interacting with screen readers and other audio-based assistive technologies. Research shows that experienced screen reader users can comprehend speech at up to 500…

Accessible Comics(also: Digital Comics Accessibility, Comic Book Accessibility)

Approaches and technologies for making comic books and graphic novels accessible to people with visual impairments. Unlike plain text, comics combine visual art, panel layouts, speech balloons, and onomatopoeia that require special consideration for non-visual access. Accessible…

Accessible Graphics(also: Accessible Images, Non-Visual Graphics)

Visual information such as charts, diagrams, maps, and illustrations that has been made perceivable and understandable to people with visual impairments through alternative formats. These formats include tactile graphics (raised line drawings, swell paper, 3D-printed models),…

Achromatopsia(also: Rod Monochromacy, Total Color Blindness, Complete Achromatopsia)

A rare inherited vision condition in which a person has little or no ability to perceive color, seeing the world primarily in shades of grey. People with achromatopsia typically also experience light sensitivity (photophobia), reduced visual acuity, and involuntary eye movements…

Adaptive Typography(also: Context-Aware Typography, Dynamic Typography)

The practice of adjusting text presentation - font size, weight, line spacing, character spacing, contrast, and colour - automatically or semi-automatically in response to the user's current needs and context. Adaptive typography goes beyond static accessibility settings by…

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…

Art Accessibility(also: Artwork Accessibility, Cultural Accessibility)

The practice of making visual art, museums, galleries, and cultural experiences accessible to people with disabilities. Art accessibility encompasses a range of approaches including tactile reproductions, audio descriptions, augmented reality overlays, accessible exhibition…

Audio-First Design(also: Audio-Centric Design, Sound-First Design)

A design approach that prioritizes audio as the primary interaction modality rather than treating it as a secondary alternative to visual interfaces. Audio-first design is particularly relevant for creating accessible educational content and AI tools for people with vision…

Auditory Graph(also: Audible Graph, Sonified Chart)

A non-visual representation of data that uses sound properties such as pitch, volume, duration, and timbre to convey the values and patterns typically shown in visual charts and graphs. Auditory graphs are an important assistive approach for making data accessible to people who…

Auto-Aim(also: Lock-On Targeting, Target Assist, Aim Assist)

An accessibility feature in games and virtual environments that helps users locate and track targets without requiring precise manual aiming. Auto-aim typically scans the environment for objects of interest and automatically adjusts the user's view or cursor to face or track the…

Barcode(also: Bar Code, QR Code, 1D Barcode)

A barcode is a machine-readable visual encoding of data — linear (one-dimensional, such as UPC or EAN) or matrix (two-dimensional, such as QR or DataMatrix codes). In a digital accessibility context, barcodes are commonly used as a lightweight way to attach identifying or…

Blind and Low Vision(also: BLV, Vision Impairment, Visual Impairment)

A broad term encompassing the spectrum of vision loss from partial sight (low vision) to complete blindness. People who are blind or have low vision experience varying degrees of visual function, and their technology needs differ accordingly. Low vision users may benefit from…

Bone Conduction Headset(also: Bone Conduction Headphones, Bone Conduction Audio)

An audio device that transmits sound vibrations through the bones of the skull directly to the inner ear, bypassing the outer and middle ear and leaving the ear canal open. For people who are blind or have low vision, bone conduction headsets are particularly valuable during…

Braille Slate and Stylus(also: Slate and Stylus, Braille Writing Frame)

A low-cost, portable tool for writing Braille by hand, consisting of a hinged metal or plastic template (slate) with rows of cells and a pointed tool (stylus) used to press dots into paper from the reverse side. The slate and stylus is the most common and affordable Braille…

Braille Textbook(also: Braille Book, Braille Edition)

A textbook transcribed into Braille for use by students and teachers who are blind. Braille textbooks are significantly larger and more expensive to produce than print textbooks, often requiring multiple volumes for a single print book. In India, government-provided Braille…

Brailler(also: Braille Writer, Perkins Brailler)

A mechanical or electronic device for writing Braille, functioning similarly to a typewriter with six keys corresponding to the six dots of a Braille cell. Braillers are significantly faster and easier to use than a slate and stylus, and produce immediately readable output…

Brightness Contrast(also: Luminance Contrast, Perceived Brightness Difference)

The difference in perceived brightness between two colors, typically between text and its background. Brightness contrast is a key factor in readability, especially for people with low vision, color vision deficiencies, or those viewing content in challenging lighting…

CCTV Magnifier(also: Closed-Circuit Television Magnifier, Video Magnifier, Desktop Video Magnifier)

An assistive device that uses a camera to capture an image of text or objects and displays it magnified on a screen, typically a television or computer monitor. CCTV magnifiers are one of the most widely used low vision aids, offering high levels of magnification, adjustable…

CVD Simulation(also: Colour Blindness Simulation, Color Vision Simulation)

A technique that transforms colours in a design to approximate how they would appear to a person with a specific type of colour vision deficiency. CVD simulations are the most widely implemented feature in accessibility design tools, available in browsers (Chrome, Firefox),…

Camera Framing(also: Photo Framing, Object Framing)

The act of positioning a camera so that the intended subject is properly captured within the image frame — not cropped, not too small, and centered enough for clear identification. Camera framing presents a significant accessibility challenge for blind and low-vision users who…

Camera Phone(also: Smartphone Camera, Mobile Camera)

A camera phone is a mobile phone equipped with a built-in image sensor, which in an accessibility context serves as the input device for a wide class of vision-based assistive applications. Modern smartphone cameras enable live scene description (Seeing AI, Be My AI), object…

Children with Vision Impairments(also: CVI, Students with Visual Impairments, Blind Students)

Children and young people who are blind or have low vision, requiring adapted educational approaches including Braille instruction, tactile learning materials, audio resources, and assistive technology. India has the world's largest population of children with vision…

Choropleth Map(also: Thematic Map, Shaded Map)

A type of thematic map in which geographic areas are shaded or patterned in proportion to a statistical variable, such as population density, income level, or unemployment rate. Darker or more intense colors typically represent higher values. Choropleth maps are widely used by…

Color Filter(also: Color Filters, Display Color Filter)

An operating-system or browser-level feature that alters how colors are rendered on screen, including grayscale, inverted colors, and filters for protanopia, deuteranopia, and tritanopia color vision deficiencies. Used by low-vision users and users with color vision deficiency…

Color Theory(also: Colour Theory)

A body of principles and guidelines for understanding how colors interact, combine, and affect perception. In accessibility contexts, color theory is important for ensuring sufficient contrast ratios, avoiding color-only information encoding, and designing for color vision…

Color Universal Design(also: CUD, Colour Universal Design)

A set of guidelines and principles developed to ensure that colour use in designs, products, and environments is accessible to people with all types of colour vision, including those with colour vision deficiency. Color Universal Design emphasizes selecting colour palettes that…

Colour Contrast(also: Color Contrast, Contrast Ratio)

The measurable difference in luminance or colour between two adjacent elements, used to determine readability and visual distinguishability. WCAG defines minimum contrast ratios (4.5:1 for normal text, 3:1 for large text at AA level) based on relative luminance calculations…

Colour Palette Generation(also: Color Palette Generation, Accessible Palette Generation)

The automated or semi-automated creation of sets of colours that are distinguishable by people with different types of colour vision deficiency while meeting aesthetic and functional design requirements. Despite its importance, colour palette generation is an underrepresented…

Colour Vision Deficiency(also: CVD, Color Blindness, Colour Blindness)

A condition in which a person has difficulty distinguishing between certain colours due to differences in the cone cells of the retina. CVD affects approximately 1 in 12 men and 1 in 200 women worldwide. It is not typically a complete inability to see colour but rather a reduced…

Colours of Confusion(also: Confusion Colors, Confusable Colours, Metameric Pairs)

Pairs or sets of colours that appear distinct to people with typical colour vision but appear identical or nearly identical to people with a specific type of colour vision deficiency. These colour pairs are predicted by CVD colour models and underlie CVD simulation tools.…

Comic Strip Conversations(also: CSC)

A visual-support technique developed by Carol Gray (1994) for autistic children and adolescents, in which a social interaction is illustrated as a short comic strip with simple stick figures, speech bubbles, thought bubbles, and colour codes for emotion. By externalising who…

Conditional Formatting

Conditional formatting is a spreadsheet feature that automatically applies visual styles — fill color, font color, bold text, icons, data bars — to cells whose values meet specified rules (for example, highlighting failing grades in red or above-average sales in green). It is…

Contrast Ratio(also: Color Contrast Ratio, Luminance Contrast Ratio)

A numerical measure of the difference in perceived brightness between two colors, expressed as a ratio ranging from 1:1 (no contrast) to 21:1 (maximum contrast, black on white). WCAG 2.2 requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text (Level…

Convergence Insufficiency(also: CI)

A binocular vision disorder in which the eyes have difficulty turning inward (converging) to focus on nearby objects, causing symptoms such as double vision, eye strain, headaches, difficulty reading, and blurred vision during close work. Convergence insufficiency affects an…

Crowd Accessibility(also: Crowdsourcing for Accessibility, Human-Powered Access Technology)

An approach that combines human intelligence with machine intelligence to create accessible content and services for people with disabilities. In crowd accessibility, micro-tasks that automated systems cannot yet perform reliably — such as describing images, identifying objects,…

Cursor Locator(also: Pointer Locator, Cursor Finder, Find My Cursor)

A software utility that helps users find the position of their mouse pointer on screen when it has been lost from view. Cursor locators typically activate through a keyboard shortcut or by detecting pointer behavior such as rapid shaking, and then draw attention to the pointer's…

Daltonization(also: Recolouring, Color Remapping)

Daltonization is a computational technique that modifies the colours in an image or on a screen to make them more distinguishable for people with colour vision deficiency (CVD). Named after John Dalton, who first described his own colour blindness in the 18th century,…

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.…

Data Descriptor(also: Training Data Descriptor)

An automated metric or feedback mechanism that characterizes the quality or properties of a dataset, particularly training images used in machine learning. In accessibility research, data descriptors provide non-visual feedback to blind users about the quality of photos they…

Data Visualization(also: Data Viz, Information Visualization)

The graphical representation of data and information using visual elements such as charts, graphs, maps, and diagrams. While data visualization is a powerful tool for communicating patterns and insights, it presents significant accessibility barriers for people with visual…

Deuteranomaly(also: Deutan Anomalous Trichromacy)

The most common type of colour vision deficiency, where the medium-wavelength (green) cone cells have a shifted sensitivity range. Deuteranomaly is a milder form of deutan CVD compared to deuteranopia, resulting in reduced ability to distinguish certain reds from greens. It…

Deuteranopia(also: Deutan Dichromacy, Green-Blind)

A type of colour vision deficiency caused by the complete absence of medium-wavelength (green) cone cells in the retina. Deuteranopia is the most common form of dichromacy, causing difficulty distinguishing red from green. Unlike protanopia, deuteranopia does not significantly…

Diagram Accessibility(also: Accessible Diagrams, Scientific Diagram Accessibility)

The practice of making visual diagrams — including scientific figures, flowcharts, organizational charts, and technical schematics — accessible to people with visual impairments, learning disabilities, or other conditions that affect visual processing. Diagram accessibility goes…

Dichromacy(also: Dichromatic Vision)

A category of colour vision deficiency in which one of the three types of cone cells is completely absent, reducing colour perception to two primary channels instead of three. The three forms are protanopia (missing red cones), deuteranopia (missing green cones), and tritanopia…

Discrimination Ellipse(also: Discrimination Ellipsoid, MacAdam Ellipse)

A region in a color space surrounding a given color within which other colors cannot be distinguished from it by an observer. In two dimensions this region forms an ellipse; in three-dimensional color spaces it becomes an ellipsoid. The size and shape of discrimination ellipses…

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…

Font Accessibility(also: Accessible Fonts, Dyslexia-Friendly Fonts)

The selection and design of typefaces to maximize readability for people with disabilities, particularly dyslexia and low vision. Research has evaluated various font properties for accessibility, finding that sans serif fonts, monospaced fonts, and fonts with distinct letter…

Font Size(also: Text Size, Type Size, Point Size)

The measurement of how large characters in a typeface are displayed, typically expressed in points (pt), pixels (px), or relative units (em, rem). Font size is a critical accessibility concern because text that is too small creates barriers for people with low vision, older…

Graph Accessibility(also: Chart Accessibility, Data Visualization Accessibility)

The practice of making charts, graphs, and other data visualisations perceivable and understandable to people with disabilities, particularly those who are blind or have low vision. Graph accessibility encompasses multiple strategies including meaningful alternative text that…

Haptic Graph(also: Haptic Chart, Force-feedback Graph)

A haptic graph is a non-visual rendering of a chart or graph — a bar chart, line graph, scatter plot, or mathematical function — that a blind or low-vision user explores by touch, typically through a force-feedback haptic device such as the PHANToM or a vibrotactile tablet.…