Glossary

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CIE L*a*b*(also: CIELAB, Lab Color Space, CIE Lab)

A perceptually uniform colour space defined by the International Commission on Illumination (CIE) in 1976, where the numerical distance between two colour values approximates the perceived visual difference between those colours. The three dimensions are L* (lightness, from…

CIE LUV(also: CIELUV, CIE 1976 L*u*v*)

A perceptually uniform color space defined by the International Commission on Illumination (CIE) that separates color into luminance (L*) and two chromaticity coordinates (u* and v*). Unlike RGB, which is tied to display hardware and not perceptually uniform, equal distances in…

CSS Box Model(also: Box Model)

A fundamental concept in CSS that describes how HTML elements are rendered as rectangular boxes with four distinct areas: content (the actual text or image), padding (space between content and border), border (the edge around the padding), and margin (space outside the border…

Classical Aesthetics(also: Classical Design Aesthetics)

A dimension of visual aesthetics in web design characterised by simplicity, clarity, orderliness, and visual cleanness. Classical aesthetic principles are rooted in early visual design traditions that prioritise clean layouts, minimal complexity, and clear organisation of…

Color Adaptive Graphics(also: Colour Adaptive Graphics)

A technique for automatically adjusting the colours in graphical content so that objects maintain similar colour contrast relative to their reference background colours, regardless of the viewing context. Unlike recolouring approaches that focus on preserving the author's…

Color Contrast(also: Colour Contrast, Contrast Ratio)

The difference in luminance between foreground text (or UI components) and their background, measured as a ratio. WCAG 2.1 requires a minimum contrast ratio of 4.5:1 for normal text and 3:1 for large text at Level AA, and 7:1 for normal text and 4.5:1 for large text at Level…

Color Gamut(also: Colour Gamut, Gamut)

The complete range of colours that can be represented or reproduced by a particular colour space, display device, or visual system. In the context of colour vision, a trichromat's gamut encompasses the full range of colours perceivable by typical human vision, while a…

Color Space(also: Colour Space, Color Model)

A mathematical model that describes the range of colours that can be represented as numerical values, typically using three or more coordinates. Common colour spaces include RGB (red, green, blue), used in digital displays; CMYK (cyan, magenta, yellow, key/black), used in…

Editorial Enunciation(also: Visual Enunciation)

A semiotic concept describing how the visual layout and organisation of an interface communicates meaning beyond the content it contains. Editorial enunciation encompasses the spatial arrangement, sizing, positioning, and visual hierarchy of interface elements — all of which…

Expressive Aesthetics(also: Expressive Design Aesthetics)

A dimension of visual aesthetics in web design characterised by creativity, originality, visual sophistication, and design ingenuity. Identified by Lavie and Tractinsky as one of two main dimensions of perceived web aesthetics, expressive designs tend to be more complex and…

Focus Indicator(also: Focus Ring, Visible Focus, Focus Outline)

A visual cue that shows which interactive element on a page or in an application currently has keyboard focus. Focus indicators are typically rendered as an outline, border, or highlight around the focused element. They are essential for keyboard users and screen magnification…

Icon(also: Icons, UI Icon)

A small graphical symbol used in graphical user interfaces (GUIs) to represent an application, file, function, or object. Icons rely on visual recognition rather than text reading, which can be both an advantage and a barrier for users with visual impairments depending on…

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…

Legibility

The visual clarity with which individual characters, words, and blocks of text can be distinguished and recognised. Legibility is influenced by font choice (sans-serif fonts are generally more legible on screen), font size (minimum 12px recommended for dyslexic users), letter…

Luminance(also: Relative Luminance)

The relative brightness of a color as perceived by the human eye, measured on a scale from 0 (black) to 1 (white). In accessibility, relative luminance is the foundation of WCAG color contrast ratio calculations, which compare the luminance of foreground text against its…

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…

Typeface Classification(also: Font Classification, Typeface Categories)

The set of broad categories used to describe and compare typefaces. The most common groupings are: serif (letters with small projecting strokes at terminals, e.g. Times, Roboto Serif), sans-serif (no terminal strokes, e.g. Helvetica, Arial, Roboto), slab serif (heavy…

Web Aesthetics(also: Visual Aesthetics, Website Aesthetics)

The study and application of visual appeal in web design, encompassing how users perceive and respond to the visual qualities of websites. Research has identified two main dimensions of web aesthetics: classical aesthetics (characterised by simplicity, clarity, and orderliness)…

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