Glossary

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Local-First Software(also: Local-First)

A software design philosophy, articulated by Kleppmann and colleagues in 2019, in which applications keep the user's primary data on local devices and treat cloud services as optional synchronization or backup layers rather than as the source of truth. Local-first systems aim to…

Localization(also: Position Estimation, Indoor Localization, User Localization)

Localization is the process of determining a user's position within an environment, typically using a combination of sensors such as GPS, inertial measurement units, BLE beacons, Wi-Fi signals, or computer vision. Accurate localization is the foundational challenge for all…

Location Awareness(also: Location-Aware Computing, Location Sensing)

The ability of a computing system to determine and respond to the physical location of a user or device, typically using GPS, Wi-Fi positioning, cellular triangulation, or other sensing technologies. In assistive technology, location awareness enables context-sensitive support…

Location-Based Game(also: LBG, Location-Based Puzzle Game, LBPG)

A location-based game (LBG) is a game whose gameplay depends on the player’s real-world physical location, typically determined via GPS, NFC, Bluetooth beacons, or QR codes. Examples include Geocaching, Ingress, Pokémon GO, and a range of urban puzzle, treasure-hunt, and tourism…

Location-Based Service(also: LBS, Location-Based Services)

A software application or platform that uses geographic position data — from GPS, Wi-Fi, Bluetooth beacons, or other localization technologies — to deliver context-aware information or functionality to users based on their physical location. In accessibility, location-based…

Locked-In Syndrome(also: LIS, Pseudocoma)

Locked-in syndrome is a rare neurological condition in which a person is fully conscious and cognitively aware but unable to move or speak due to complete paralysis of nearly all voluntary muscles, often resulting from a brainstem stroke or injury. People with locked-in syndrome…

Locomotion(also: VR Locomotion)

Methods by which users navigate and move through virtual environments in VR. Common locomotion techniques include free-roam (physical walking that maps to virtual movement), joystick-based continuous movement, teleportation (pointing to a destination and instantly moving there),…

Locomotion Technique(also: VR Locomotion, Virtual Travel Technique)

A locomotion technique is a method for navigating or moving through a virtual environment in virtual reality (VR). Because physical space is limited and many users are seated, locomotion techniques simulate travel without requiring real-world walking. Common approaches include…

LogMAR(also: Logarithm of the Minimum Angle of Resolution)

A standardised scale for measuring visual acuity based on the logarithm (base 10) of the minimum angle of resolution, used in the Bailey-Lovie eye chart and widely adopted in clinical vision research. A logMAR value of 0.0 corresponds to 20/20 (6/6) vision, with higher values…

Logical Control(also: Indirect Control)

An interaction paradigm where the user accesses specific functions supported by an application indirectly, typically by selecting from a presented set of options rather than performing the action directly. Examples include scanning through a menu of commands, using keyboard…

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…

Logical Navigation(also: Structural Navigation, Semantic Navigation)

A non-visual navigation strategy in which a user moves through a web page by its semantic structure — jumping between heading levels, ARIA landmarks, skip links, form fields, or other role-tagged regions — rather than reading the content sequentially or sampling fragments by…

Logical Reading Order(also: Reading Sequence, Programmatic Reading Order)

The sequence in which content within a document is presented to assistive technologies, which should match the intended logical flow of the content as a human reader would understand it. In PDFs, the logical reading order is determined by the tag tree structure, not the visual…

Logocentrism

In captioning studies, the systematic prioritization of speech and spoken language over non-speech sounds in captioning practices and technologies. Logocentrism in captioning manifests as speech captions receiving more attention, resources, and technical development than…

Lombard Effect(also: Lombard Reflex, Lombard Response)

The involuntary tendency of speakers to increase the intensity, duration, and fundamental frequency of their speech when communicating in noisy environments. Named after French otolaryngologist Étienne Lombard who first described the phenomenon in 1911, the effect involves…

Loneliness(also: Perceived Social Isolation)

The subjective feeling of being alone or disconnected from others, regardless of the actual quantity of social contacts a person has. Loneliness differs from social isolation in that it reflects perceived rather than objective social disconnection—a person can feel lonely in a…

Long Description(also: Extended Description, longdesc)

A detailed textual description of an image or other non-text content that goes beyond the brief summary provided by alt text. Long descriptions are used for complex images such as charts, diagrams, infographics, or detailed illustrations where a short alt text cannot convey all…

Long Tail(also: Long-tail Distribution, Long-tail Participation)

A statistical distribution in which a small number of items or participants account for the majority of the total, while a very long list of lower-frequency items collectively make up the remainder. The term was popularised by Chris Anderson in reference to online retail, but it…

Longdesc(also: Long Description, longdesc Attribute)

An HTML attribute historically used to provide extended descriptions for images that require more detail than can fit in an alt attribute. The longdesc attribute contained a URL pointing to a separate page or anchor with the full description. While part of HTML 4.01 and…

Longitudinal Study(also: Long-Term Study)

A research method that involves repeated observations or measurements of the same subjects over an extended period of time. In accessibility and reading support research, longitudinal studies are important for evaluating the sustained impact of interventions, tracking skill…

Look to Speak

A free Android application developed by Google Creative Lab that enables people with speech and motor impairments to communicate by selecting images or pre-written phrases using eye movements detected by the smartphone's front-facing camera. Users navigate by looking left,…

Lookout(also: Google Lookout)

An Android accessibility application developed by Google that uses the smartphone camera and machine learning to identify objects, read text, scan documents, and describe surroundings for blind and partially sighted users. Lookout can identify currency, read food labels,…

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…

Loss Aversion

A cognitive bias in which people experience the pain of losing something more intensely than the pleasure of gaining something of equal value. In the context of technology accessibility and aging, loss aversion significantly influences older adults' adoption of digital tools,…

Loss of Obscurity(also: Loss of anonymity)

A concept introduced by Thomas J. Carroll in his 1961 book "Blindness: What It Is, What It Does, and How to Live with It," in which he identified twenty distinct losses that accompany the onset of blindness. Loss of obscurity refers to the unavoidable conspicuousness of carrying…

Lost Generation

In ADHD and autism discourse, the term refers to adults — particularly women, minority genders, and people of colour — who went undiagnosed as children due to gendered diagnostic criteria, systemic medical bias, and the historical exclusion of non-white, non-male bodies from…

Loudness Recruitment(also: Recruitment, Hyperacusis-like Recruitment)

Loudness recruitment is a common consequence of sensorineural hearing loss in which the range between 'just audible' and 'uncomfortably loud' sounds is compressed — quiet sounds are harder to hear, but sounds above threshold grow louder more rapidly than in a typical listener.…

Low Bandwidth Input(also: Limited Input, Reduced Bandwidth Input)

A category of human-computer interaction where the user can only produce a very small number of distinct signals — typically one to four — when communicating with a computer. Low bandwidth input characterizes users with severe motor and speech impairments, such as those with…

Low Literacy(also: Limited Literacy, Functional Illiteracy)

A level of reading and writing ability that is below what is typically needed to function effectively in everyday situations requiring text comprehension. Low literacy may result from limited educational opportunities, learning disabilities, cognitive disabilities, or reading in…

Low Vision(also: Partial Sight, Visual Impairment)

A visual condition in which a person has significant vision loss that cannot be fully corrected with glasses, contact lenses, medication, or surgery, but retains some usable vision. People with low vision may have reduced visual acuity, limited field of vision, or difficulty…

Low Vision(also: Partial Sight, Partially Sighted)

A visual impairment that cannot be fully corrected by glasses, contact lenses, medication, or surgery, but where some usable vision remains. Low vision encompasses a wide range of conditions and severity levels, typically defined as visual acuity between 20/70 and 20/400 in the…

Low and Middle Income Countries(also: LMICs, Developing Countries, Global South)

A World Bank classification for countries with gross national income per capita below a defined threshold, encompassing low income and lower-middle income economies. In accessibility contexts, LMICs present distinct challenges including limited investment in accessible…

Low vision(also: Partial sight, Visual impairment)

A level of visual impairment that cannot be fully corrected with standard glasses, contact lenses, medication, or surgery, but retains some usable vision — distinguishing it from total blindness. Low vision encompasses a range of conditions affecting acuity, visual field,…

Low- and Middle-Income Countries(also: LMIC, LMICs, developing countries)

Countries classified by the World Bank as having lower gross national income per capita, typically facing greater resource constraints in healthcare, education, and technology infrastructure. In accessibility contexts, LMICs present unique challenges including limited…

Low-Barrier Access(also: Low-Barrier Technology)

Technology or services designed to minimize obstacles to initial use, including cost, setup complexity, training requirements, and technical prerequisites. Low-barrier access is particularly important for people with temporary or newly acquired disabilities who may need…

Low-Fidelity Prototype(also: Low-Fi Prototype, Lo-Fi Prototype, Paper Prototype)

A rough, inexpensive representation of a design - typically paper sketches, cardboard models, or wireframes - used early in the design process to explore concepts without investing in polished artefacts. Low-fidelity prototypes lower the barrier to critique and change, which is…

Low-Fidelity Prototyping(also: Lo-Fi Prototyping, Paper Prototyping)

A design method that uses simple, inexpensive materials to create quick, rough representations of a product or interface for early-stage testing and feedback. Traditional lo-fi prototyping relies heavily on visual methods such as sketches, storyboards, and paper mockups, which…

Low-Functioning Autism(also: LFA, Classic Autism, Level 3 Autism)

A descriptor historically used to characterize individuals with autism spectrum disorder who have significant support needs, including limited or no verbal communication, intellectual disability, and difficulty with daily living skills. The term is increasingly considered…

Low-Incidence Disability(also: Low-Prevalence Disability)

A disability that occurs relatively rarely in the general population, such as blindness, deafblindness, or certain developmental conditions. Low-incidence disabilities present unique challenges for research, education, and technology development because affected individuals are…

Low-Resource Setting(also: Resource-Limited Setting, Resource-Constrained Environment)

A context characterized by limited financial resources, infrastructure, trained professionals, and technological capacity that affects the availability and sustainability of services including healthcare and assistive technology. Low-resource settings present unique challenges…

Low-Resource Sign Language

A sign language for which standardised corpora, training data, technical infrastructure, and institutional support are limited compared to 'high-resource' sign languages like American Sign Language (ASL) or German Sign Language (DGS). Low-resource sign languages — such as Bangla…

Low-Tech AAC(also: No-Tech AAC, Unaided AAC)

Augmentative and alternative communication methods that require no or minimal technology, including communication boards, picture cards, letter boards, eye-pointing frames, sign language, and gestures. Low-tech AAC is often more immediately accessible, sustainable, and…

Low-Tech Accessibility(also: Low-Tech Accommodations, Low-Tech Solutions)

Accessibility solutions that use simple, inexpensive materials and methods rather than advanced technology to support people with disabilities in completing tasks. Examples include tactile guides made from tape or magnets on equipment, raised markings for orientation, notches…

Low-Vision Rehabilitation(also: LVR, Vision Rehabilitation)

A multidisciplinary service aimed at helping individuals with reduced vision regain functional independence in daily life. LVR combines assistive technologies, guided training sessions, and adaptive strategies tailored to each person's visual abilities and needs. Programs…

Low-Vision Therapist(also: LVT, Low-Vision Specialist, Vision Rehabilitation Therapist)

A certified professional who works with people with low vision to develop adaptive strategies for daily living, optimize use of residual vision, and provide training with assistive devices. LVTs are part of a multidisciplinary rehabilitation team that may include…

Lower Limb Impairment(also: Lower Extremity Impairment, Lower Body Impairment)

Reduced function in one or both legs or feet due to conditions such as amputation, paralysis, muscular disorders, or joint conditions. In VR accessibility, lower limb impairment primarily affects locomotion methods—free-roam VR requiring physical walking is inaccessible, while…

Lubben Social Network Scale(also: LSNS, LSNS-6)

A validated screening instrument used to assess social isolation risk in older adults by measuring the size and closeness of their social networks. The abbreviated LSNS-6 version contains six items covering family and friend networks, asking about the number of relatives and…

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…

Luminance Contrast(also: Brightness Contrast)

The difference in perceived brightness between two adjacent surfaces or objects, as opposed to color contrast which involves differences in hue. Luminance contrast is particularly important for people with low vision, as many have difficulty distinguishing colors but can detect…

Luminous Efficiency Function(also: LEF, Spectral Luminous Efficiency Function, V(lambda))

A function that describes how the human visual system converts light intensity at different wavelengths into perceived brightness. The standard LEF used in WCAG contrast ratio calculations is based on a "standard observer" with typical colour vision. However, people with CVD —…