Glossary

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Layer-wise Relevance Propagation(also: LRP)

Layer-wise Relevance Propagation (LRP) is an explainable AI technique that attributes a neural network's prediction back to its input features by propagating relevance scores layer by layer from the output toward the input. Unlike gradient-based saliency methods, LRP…

Layout Customization(also: Visual Layout Control)

The ability to modify the spatial arrangement and visibility of visual elements within a video or interface. In video accessibility for ADHD, layout customization allows viewers to choose which visual elements to display (speaker, content, overlays) and how they are sized and…

Layout Table(also: Presentational Table)

An HTML table element used to control the visual positioning of content on a web page rather than to present tabular data. Layout tables were a common web design technique before CSS became widely supported, but their use is now considered a significant accessibility barrier.…

Leadership of the Most Affected

A core principle of disability-justice organising that positions people most directly affected by a problem — those with the most at stake and the most lived expertise — as the leaders of work aimed at solving it, rather than as consultants, testers, or recipients of others'…

Leap Motion(also: Leap Motion Controller)

A compact infrared hand-tracking sensor that uses binocular cameras to detect and track finger and hand positions in three-dimensional space without physical contact. In accessibility research, Leap Motion controllers have been used to create touchless interfaces for people with…

Leapfrog Technology(also: Leapfrogging)

The adoption of advanced or cutting-edge technology in contexts that skipped intermediate technological stages, bypassing legacy infrastructure to achieve modern capabilities directly. In assistive technology, leapfrogging refers to the potential for Global South countries to…

Learnability

A usability attribute measuring how easy it is for users to accomplish basic tasks the first time they encounter a design. High learnability means new users can quickly become productive with a system. For accessibility, learnability is particularly important because users with…

Learned Helplessness

A psychological condition in which a person comes to believe they are unable to perform tasks or control outcomes, often resulting from prolonged over-assistance or lack of opportunity to attempt tasks independently. In disability contexts, learned helplessness can develop when…

Learning Design(also: IMS Learning Design, IMS LD)

A specification from IMS Global Learning Consortium (based on the Educational Modeling Language) that provides a framework for describing the structure and sequence of learning activities, roles, and environments in educational scenarios. Learning Design enables the separation…

Learning Disability(also: Specific Learning Disability, Learning Disorder)

A neurological condition that affects the brain's ability to receive, process, store, respond to, or communicate information. Learning disabilities include dyslexia (reading), dyscalculia (mathematics), dysgraphia (writing), and other specific processing difficulties. Learning…

Learning Management System(also: LMS)

A software platform used to create, deliver, manage, and track educational content and learning activities. Common examples include Blackboard, Moodle, Canvas, and Google Classroom. In the context of accessibility, LMS platforms are critical because they serve as the primary…

Learning Object(also: LO, Reusable Learning Object, RLO)

A self-contained, reusable unit of educational content that can be independently accessed, combined with other learning objects, and delivered across different learning management systems. Learning objects can include text, multimedia, interactive exercises, assessments, or any…

Learning Object Metadata(also: LOM, IEEE LOM)

A data model used to describe learning resources, standardized by IEEE (IEEE 1484.12.1). Learning Object Metadata defines a set of elements organized into categories including general, lifecycle, technical, educational, and rights information. For accessibility, LOM is…

Learning Vector Quantization(also: LVQ)

A supervised machine learning algorithm used for pattern classification, commonly applied in brain-computer interface systems to classify EEG signals. LVQ works by creating a set of reference vectors (codebook) that represent decision boundaries between different classes of…

Learning by Doing(also: Incidental Learning, Learning-While-Doing)

Learning by doing is a pedagogical and interface design principle in which skills are acquired through the process of performing tasks rather than through separate, explicit instruction. In human-computer interaction, interfaces designed around this principle enable users to…

Leber Hereditary Optic Neuropathy(also: LHON)

A maternally inherited genetic condition that causes sudden or rapid loss of central vision, typically affecting young adults between the ages of 15 and 35. LHON results from mutations in mitochondrial DNA that damage the optic nerve, leading to significant bilateral central…

Lecture Accessibility(also: Accessible Lectures, Accessible Educational Media)

The practice of designing and delivering lectures and associated educational materials so that they are usable by students with disabilities, including those who are blind, have low vision, are deaf, or have other impairments. Lecture accessibility encompasses multiple…

Lecture Captioning(also: Classroom Captioning, Lecture Transcription)

The real-time or post-production conversion of spoken lecture content into text, displayed to students during or after a class session. Lecture captioning can be performed by human captioners (such as CART providers), by automatic speech recognition software, or by a combination…

Lecture Capture(also: Lecture Recording, Classroom Recording)

The process of recording classroom lectures, presentations, or educational sessions using video, audio, and screen capture technology for later review by students. Lecture capture systems range from simple single-camera recordings to multi-camera setups that capture the…

Lee Silverman Voice Treatment(also: LSVT, LSVT LOUD)

An evidence-based speech therapy programme originally developed for individuals with Parkinson's disease that focuses on increasing vocal loudness as the primary mechanism for improving overall speech clarity. LSVT trains patients to "think loud" and speak with greater effort,…

Legal Blindness(also: Legally Blind)

A level of vision loss defined in many countries as visual acuity of 20/200 or less in the better eye with best correction, or a visual field of 20 degrees or less. Legal blindness does not necessarily mean total blindness — many legally blind people have some residual or…

Legal blindness(also: Legally blind)

A level of visual impairment defined in many jurisdictions as visual acuity of 20/200 or worse in the better eye with best correction, or a visual field of 20 degrees or less. Legal blindness is an administrative threshold used to determine eligibility for disability benefits…

Legally Blind(also: Legal Blindness)

A legal classification of visual impairment used to determine eligibility for government benefits, rehabilitation services, and disability accommodations. In the United States, legal blindness is defined as visual acuity of 20/200 or worse in the better eye with best correction,…

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…

Legion:Scribe(also: Scribe, Legion Scribe)

A crowd captioning system developed at the University of Rochester that enables multiple non-expert typists to collectively produce real-time captions by simultaneously typing partial transcriptions of speech, which are then automatically aligned and merged into a single…

Legitimate Peripheral Participation(also: LPP)

A concept from Jean Lave and Etienne Wenger's situated-learning theory describing how newcomers join a community of practice by first participating in peripheral, lower-stakes activities and gradually moving toward full, central participation as they acquire the practices and…

Letter Reversal(also: Mirror Writing, Character Reversal)

A reading or writing difficulty where visually similar letters are confused or substituted for one another, such as swapping b for d, or p for q. Letter reversal is commonly associated with dyslexia and can significantly impact word recognition and reading comprehension. In…

Leukodystrophy(also: Leukodystrophies)

Leukodystrophy is a group of rare, progressive, metabolic, genetic diseases that affect the brain, spinal cord, and peripheral nerves by damaging the white matter (myelin sheath) that insulates nerve fibers. Symptoms can include difficulty with movement and coordination, speech…

Level of Detail(also: LOD)

A technique in computer graphics and information design where the amount of detail presented varies based on context, typically distance or user interaction. In 3-D environments, objects farther from the viewer are rendered with less geometric detail to improve performance. In…

Levenshtein Distance(also: Edit Distance)

A metric that measures the minimum number of single-character edits (insertions, deletions, and substitutions) needed to transform one string into another. In accessibility research, Levenshtein distance is used to quantify how much users modify AI-generated or existing text,…

Lewy Body Dementia(also: LBD, Dementia with Lewy Bodies, DLB)

A type of progressive dementia caused by abnormal protein deposits called Lewy bodies in the brain. Lewy body dementia affects thinking, movement, behavior, and mood, and is the third most common cause of dementia after Alzheimer's disease and vascular dementia. Symptoms include…

Lexical Access(also: Lexical Retrieval, Word Access)

The cognitive process of retrieving words from the mental lexicon during language production or comprehension. Lexical access involves activating the phonological, semantic, and syntactic properties of a word stored in memory. Disorders of lexical access, such as those seen in…

Lexical Chain(also: Lexical Chaining, Lexical Cohesion)

A sequence of semantically related words running through a text — for example, "doctor", "hospital", "nurse", "patient" — connected by relations like synonymy, hypernymy, or hyponymy. Lexical chains capture the topical coherence of a document and are used in readability…

Lexical Elaboration(also: Vocabulary Elaboration)

A text adaptation technique that makes content more accessible by adding explanatory information for complex or unfamiliar words, rather than replacing or removing them. Unlike text simplification, which rewrites content using simpler language, lexical elaboration preserves the…

Lexical NMS(also: Lexical Non-Manual Sign)

Non-manual signs that are an integral part of a specific sign's production, required to distinguish it from other signs that share the same manual component. For example, the ASL sign for "NOT YET" includes a hand gesture combined with the tongue touching the lower lip and a…

Lexical Semantics

The branch of linguistics concerned with the meaning of words and the relationships between word meanings, including synonymy, antonymy, and the semantic roles words can fill in sentences. In assistive technology, lexical semantic knowledge is used in AAC systems and text…

Lexical Signing(also: Lexical Sign, LS)

In American Sign Language and related signed languages, the production of meaning by syntactically combining individual lexical signs drawn from the language's vocabulary — analogous to combining words into sentences in a spoken or written language. Lexical signing is contrasted…

Lexical Simplification(also: Word-Level Simplification)

A form of text simplification that focuses on replacing complex, uncommon, or technical words with simpler, more familiar alternatives. Lexical simplification is particularly relevant for readers with limited vocabulary, including people who are deaf or hard of hearing (for whom…

Lexile Framework(also: Lexile, Lexile Measure)

A commercial readability framework developed by MetaMetrics that places both texts and readers on a common scale — the Lexile measure — to support matching readers with materials at an appropriate level of challenge. A text's Lexile measure is computed from sentence length and…

Lexile Score(also: Lexile Measure, Lexile Level)

A standardised measure of text complexity and reading ability, expressed on the Lexile scale (roughly 0L to 1600L+). A Lexile text measure reflects sentence length and word frequency; a Lexile reader measure reflects the reader's ability. For accessibility, Lexile scores provide…

LiDAR(also: Light detection and ranging, Laser scanning)

A remote sensing technology that measures distances by emitting laser pulses and analysing the reflected light, producing precise three-dimensional point clouds of the surrounding environment. In accessibility, LiDAR has multiple applications: it is used to assess pedestrian…

Liberatory access(also: Liberation-oriented access)

An approach to accessibility that goes beyond inclusion and assimilation to challenge the broader conditions of ableism and exclusion that create inaccessibility in the first place. Coined by disability justice activist Mia Mingus, liberatory access strives not just to help…

Libras(also: Brazilian Sign Language, Língua Brasileira de Sinais)

The official sign language of the Deaf community in Brazil, recognized by Brazilian federal law (Law No. 10.436/2002) as a legitimate means of communication and expression. Libras has its own grammar, syntax, and linguistic structure distinct from spoken Brazilian Portuguese. It…

Librosa

An open-source Python library for audio and music signal analysis, widely used in music-information retrieval and accessibility research to extract low-level acoustic features such as tempo, RMS energy, spectral centroid, zero-crossing rate, chroma, and mel-frequency cepstral…

Life Story Work(also: Life Story, Biography Work, Digital Biography)

A person-centered approach to care that involves gathering and sharing information about an individual's life history, preferences, relationships, and experiences. In dementia care, life story work helps caregivers see the person behind the condition and supports meaningful…

Lifelogging(also: Life Logging, Digital Lifelogging)

Lifelogging is the practice of automatically and continuously capturing data about a person's daily life using sensors, cameras, GPS, and other digital tools, typically worn or carried by the individual. In the context of accessibility, lifelogging data can be used to build…

Lifestyle Modelling(also: Lifestyle Monitoring, Lifestyle Modeling)

Lifestyle modelling is the correlation of a person's observed day-to-day activities — sleeping, eating, moving between rooms, interacting with objects — with inferences about their well-being, usually using data from ambient sensors in the home. In accessibility and…

Light Sensitivity(also: Photophobia, Photosensitivity)

An abnormal sensitivity to light that causes discomfort, pain, or visual disruption. Many people with low vision experience light sensitivity, which can be exacerbated by bright overhead lighting, backlit screens, glare from reflective surfaces, and high-contrast environments.…

Lighthouse(also: Google Lighthouse, Chrome Lighthouse)

An open-source automated tool developed by Google for auditing web page quality, including performance, accessibility, SEO, and progressive web app compliance. Lighthouse runs in Chrome DevTools, as a browser extension, or via command line, and produces scores from 0-100 for…

Likert Scale(also: Likert-Type Scale)

A psychometric rating scale commonly used in surveys and usability studies where respondents indicate their level of agreement or satisfaction on a symmetric scale, typically with 5 or 7 points ranging from "strongly disagree" to "strongly agree." Likert scales are standard…