Glossary

Search results

Optical Flow

A computer vision method that estimates the apparent motion of objects between consecutive video frames by tracking pixel displacement patterns. Optical flow calculates velocity vectors showing movement direction and speed across an image. In assistive technology, optical flow…

Optical Music Recognition(also: OMR)

Computer vision technology that automatically converts images of printed or handwritten music notation into machine-readable digital formats such as musicXML. OMR is analogous to OCR (Optical Character Recognition) for text. While OMR can potentially streamline the creation of…

Opticon(also: Optical-to-Tactile Converter)

An early assistive technology device developed by Dr. James Bliss in the 1960s that converts printed text into a tactile vibrating pattern that can be read with the fingertip. The Opticon uses a small camera to scan printed characters and reproduces them as patterns of vibrating…

Option Repertoire

A type of technology repertoire where a person has multiple tools that can each independently address the same access barrier, choosing between them based on context. For example, a person might use fidget toys, background music, or noise-canceling headphones to manage sensory…

OrCam(also: OrCam MyEye, OrCam Read)

A family of wearable assistive devices made by OrCam Technologies that use a camera and on-device AI to read printed text aloud, identify faces and products, and recognize colors and banknotes for blind and low vision users. The flagship OrCam MyEye clips magnetically to the arm…

Oral Language(also: Expressive Oral Language, Spoken Language)

Oral language is the system of spoken communication comprising articulation (producing speech sounds), vocabulary (tact or naming), grammar and linguistic structure, and pragmatic or conversational use. It is distinct from written language and from augmentative communication…

Oral Motor Impairment(also: Oral-Motor Dysfunction, Oromotor Impairment)

A condition affecting the muscles and movements of the mouth, jaw, lips, and tongue that are involved in speech production, feeding, and swallowing. Oral motor impairments can result from neurological conditions such as cerebral palsy, stroke, or traumatic brain injury, and may…

Oralism(also: Oral Method, Oral Education)

An educational philosophy and approach for deaf and hard of hearing individuals that emphasizes spoken language and lip-reading over the use of sign language. Historically, oralism dominated deaf education following the 1880 Milan Conference, which effectively banned sign…

Orca(also: GNOME Orca)

A free, open source screen reader for the GNOME desktop environment on Linux and Unix-like operating systems. Orca provides access to graphical applications through speech synthesis, braille output, and magnification. It uses the AT-SPI (Assistive Technology Service Provider…

Order-Irrelevance Principle

The counting principle that the order in which objects are counted does not affect the total — counting the same set of objects in any sequence will yield the same number. This concept, while intuitive for most people, is often not understood by learners with dyscalculia, who…

Organizations of Persons with Disabilities(also: OPD, OPDs, Disabled Persons Organizations)

Organizations that are led, directed, and governed by people with disabilities, where the majority of members and leadership positions are held by disabled people. OPDs are distinct from organizations "for" people with disabilities that may be run by non-disabled people. Under…

Orientation and Mobility(also: O&M)

A professional field and set of skills that enable blind and visually impaired people to travel safely and independently in their environments. Orientation refers to understanding one's position in space relative to landmarks and destinations, while mobility refers to the…

Orientation and mobility(also: O&M)

A professional discipline and set of skills that enable people with visual impairments to travel safely and independently through their environment. Orientation refers to understanding one's position relative to the surrounding environment using sensory cues, landmarks, and…

Orthographic Depth(also: Orthographic Transparency, Spelling Transparency)

A measure of how consistently a written language maps between its spelling (graphemes) and pronunciation (phonemes). Shallow or transparent orthographies like Spanish, Finnish, and Italian have highly consistent letter-to-sound correspondences, while deep or opaque orthographies…

Orthographic Depth(also: Orthographic Transparency, Spelling Transparency)

The degree of consistency in the relationship between letters (graphemes) and sounds (phonemes) in a writing system. Languages with shallow or transparent orthography — like Finnish, Spanish, and Italian — have highly consistent letter-to-sound mappings, meaning words are…

Orthographic Projection(also: Parallel Projection)

A method of representing a three-dimensional object in two dimensions by projecting its features onto a flat plane using parallel lines perpendicular to that plane, eliminating perspective distortion. In accessibility contexts, orthographic projections (typically top, front, and…

Orthography(also: Spelling System, Writing System)

The conventional spelling system of a language, including the rules and patterns that govern how sounds (phonemes) are represented by written symbols (graphemes). Languages vary in orthographic depth: shallow or transparent orthographies like Spanish and Italian have consistent…

Orthosis(also: Orthotic, Orthotic Device, Brace)

An externally applied medical device used to modify the structural and functional characteristics of the neuromuscular and skeletal system. Orthoses support, align, prevent, or correct deformities and improve the function of movable parts of the body. Common types include ankle…

Orthotics(also: Orthosis, Orthoses, Orthotic Device)

Externally applied devices used to modify the structural and functional characteristics of the neuromuscular and skeletal systems — including braces, splints, and supports for the spine, limbs, hands, feet, and neck. Orthoses stabilize joints, correct alignment, redistribute…

Osteoarthritis(also: OA, Degenerative Joint Disease)

The most common form of arthritis, caused by progressive breakdown of the cartilage that cushions the ends of bones. Osteoarthritis produces joint pain, stiffness, swelling, and reduced range of motion, most often in the hands, knees, hips, and spine. For digital accessibility,…

Outcome-Based Education(also: OBE, Standards-Based Education)

An educational approach that focuses on measuring student achievement through specific, predetermined outcomes or competencies rather than on the process of learning itself. In disability and special education contexts, outcome-based education can be controversial because it…

Outlier detection(also: Anomaly detection, Novelty detection)

An algorithmic technique that identifies data points or behaviors that deviate significantly from expected patterns, used in fraud detection, quality assurance, CAPTCHAs, and crowd labor platforms. People with disabilities are disproportionately flagged as outliers because…

Over-Assistance(also: Over-Helping, Excessive Assistance)

The tendency of caregivers, family members, or support providers to complete tasks for a person with a disability rather than allowing them to perform the tasks independently, even when the person is capable. Over-assistance often stems from time pressure, concern about safety,…

Over-rotation(also: Rotation overshoot, Turn overshoot)

The phenomenon where a person rotates beyond a target heading angle when following a turn instruction, typically caused by the delay between perceiving a stop signal and physically halting the rotation. In navigation assistance for blind users, over-rotation is a systematic…

Overcompensation(also: Positive overcorrection, Debiasing overcorrection)

In the context of AI bias and disability representation, overcompensation (also called positive overcorrection) refers to a failure mode in which a model's debiasing mechanisms over-adjust away from negative portrayals, producing excessively or unrealistically positive…

Overlap Error(also: Key Overlap Error, Simultaneous Key Press Error)

A typing error that occurs when two keys are pressed down at the same time, typically when a finger accidentally activates an adjacent key while moving toward the intended key, or when a user's hand rests on a key unintentionally. Overlap errors are particularly common among…

Overlay Detection(also: Overlay Recognition)

The process of automatically identifying graphical or textual elements overlaid on top of video content, such as pop-up graphics, watermarks, banners, subtitles, logos, and text annotations. Overlay detection uses computer vision techniques including edge detection, shape…

Overlay Fact Sheet(also: Accessibility Overlay Fact Sheet)

A public document signed by over 600 accessibility experts, lawyers, and contributors to web accessibility guidelines that critically evaluates the claims made by accessibility overlay vendors. The fact sheet argues that overlays do not adequately address the needs of disabled…

Overselectivity(also: Stimulus Overselectivity, Overselective Attention)

A learning challenge in which an individual attends to only one or a few features of a stimulus while ignoring other relevant features, resulting in an inability to discriminate between stimuli that share some characteristics. For example, a child who is overselective might…

Overshoot(also: Cursor Overshoot, Target Overshoot)

In pointing device interaction, the phenomenon where the cursor travels beyond the intended target before the user can stop it, requiring corrective movements back toward the target. Overshoot is measured as the maximum distance traveled beyond the target as a percentage of the…

Overview+Detail(also: Overview and Detail)

A visualization interaction paradigm that presents a smaller overview view alongside a larger detail view, letting users navigate the whole while inspecting a part. Common in maps, document readers, and data dashboards. For low-vision users, overview+detail can support spatial…

Oxygen Desaturation(also: Hypoxemia, O2 Desaturation)

A drop in blood oxygen saturation levels below normal ranges, which can occur during physical exertion in people with chronic respiratory conditions like COPD. Oxygen desaturation during exercise is a medical concern that may require the person to stop, rest, and practice…