Glossary

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P300(also: P3, P300 Component, P3b)

The P300 is an event-related potential (ERP) component — a positive voltage deflection in EEG brain signals that peaks approximately 300 milliseconds after a person perceives a rare or task-relevant stimulus among frequent non-target stimuli. It is named for its polarity…

PANAS(also: Positive and Negative Affect Schedule, PANAS Scale)

PANAS (Positive and Negative Affect Schedule) is a validated psychological instrument for measuring emotional states, consisting of two 10-item scales measuring positive affect (PA) and negative affect (NA). Positive affect terms include enthusiastic, interested, determined,…

PC-Talker(also: PCTalker)

A Windows screen reader developed by the Japanese company KGS Corporation, widely used by blind and low-vision users in Japan. PC-Talker provides speech output for Windows applications and the web and integrates with the companion Net Reader Neo browser tailored to…

PDF Accessibility(also: Accessible PDF, PDF A11y)

The practice of creating PDF documents that can be effectively used by people with disabilities, including those who use screen readers, keyboard navigation, magnification, or other assistive technologies. Accessible PDFs require proper document structure (tag trees with…

PDF Form(also: PDF Fillable Form, Interactive PDF Form, AcroForm)

A PDF document that contains interactive form fields — text boxes, checkboxes, radio buttons, signatures, dropdowns — that users can fill in and submit electronically, rather than a static PDF meant only for reading. PDF forms are widely used for government applications,…

PDF Remediation(also: PDF Tagging, PDF Accessibility Remediation, Document Remediation)

The process of adding structural tags to an existing PDF document to make it accessible to assistive technologies such as screen readers. Remediation involves identifying logical content elements (headings, paragraphs, lists, tables, images), assigning appropriate tags,…

PDF Tagging(also: Tagged PDF, PDF Tags)

The process of adding a logical structure tree to a PDF so that assistive technologies can interpret the document's content, reading order, and semantics independently of its visual layout. Tags label each piece of content with its role — heading, paragraph, list item, figure,…

PDF/UA(also: ISO 14289, Universal Accessibility for PDF)

The international standard (ISO 14289) for accessible PDF documents. PDF/UA defines requirements for PDF content, PDF readers, and assistive technology to ensure accessible interaction with PDF documents. It builds on the existing PDF tag structure and requires proper reading…

PHANTOM(also: PHANTOM Omni, PHANTOM Desktop, SensAble PHANTOM)

A family of force-feedback haptic devices originally developed by SensAble Technologies (now part of 3D Systems). PHANTOM devices use a pen-like stylus that users grasp while motors apply forces to create the sensation of touching virtual objects or being guided along…

PICTIVE(also: Plastic Interface for Collaborative Technology Initiatives through Video Exploration)

PICTIVE is a participatory paper-prototyping technique introduced by Michael Muller at CHI 1991, in which end users and designers jointly build low-fidelity interface prototypes using pre-cut paper UI elements (buttons, menus, text fields, icons), sticky notes, pens, and tape,…

PLA Filament(also: Polylactic Acid Filament, PLA)

A biodegradable thermoplastic derived from renewable resources like corn starch, commonly used as the default material in consumer-grade 3D printers. PLA is easy to print with, produces minimal warping, and is available in many colors, but it has lower heat resistance and impact…

POMDP(also: Partially Observable Markov Decision Process)

A Partially Observable Markov Decision Process (POMDP) is a mathematical framework for modelling decision-making in situations where an agent cannot fully observe the state of its environment. In accessibility research, POMDPs are used to model how people with visual impairments…

POUR

The four foundational principles of WCAG: Perceivable (information must be presentable to users in ways they can perceive), Operable (user interface components must be operable), Understandable (information and operation of the user interface must be understandable), and Robust…

POUR Principles(also: POUR, Four Principles of Accessibility)

The four foundational principles of the Web Content Accessibility Guidelines (WCAG): Perceivable, Operable, Understandable, and Robust. Perceivable means information must be presentable in ways users can perceive (e.g., alt text for images, captions for video). Operable means…

PRISMA(also: Preferred Reporting Items for Systematic Reviews and Meta-Analyses)

A standardized methodology and reporting guideline for conducting systematic literature reviews and meta-analyses. PRISMA provides a structured framework including a checklist and flow diagram that documents how studies are identified, screened, assessed for eligibility, and…

PRISMA-ScR(also: PRISMA Extension for Scoping Reviews)

PRISMA-ScR is the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews - a 20-item checklist and flow diagram that standardises how scoping reviews are reported. It adapts the PRISMA framework (designed for systematic reviews) to the…

PS5 Access Controller(also: PlayStation Access Controller, Access Controller)

Sony's highly customisable controller for PlayStation 5, released in 2023 and designed for players with limited motor control. It has a flat disc layout with interchangeable button caps and analog stick attachments, 3.5 mm expansion ports for external switches, and…

PTSD(also: Post-traumatic stress disorder, Post-traumatic stress)

A psychiatric condition that can develop after exposure to traumatic events, characterized by intrusive memories, avoidance of trauma-related stimuli, negative changes in mood and cognition, and heightened arousal responses including hypervigilance and exaggerated startle. In…

PVI(also: People with Visual Impairments, Person with Visual Impairment, Persons with Visual Impairments)

An abbreviation widely used in HCI and accessibility research for "people with visual impairments," a person-first umbrella term that includes people who are blind, legally blind, or have low vision. PVI is often used interchangeably with BVI ("blind and visually impaired") and…

Pa11y

An open-source automated accessibility testing tool that runs from the command line and in continuous-integration pipelines. Pa11y can drive either axe-core or HTML CodeSniffer as its underlying rule engine, returning JSON-formatted results classified by severity (critical,…

Pacing Aid(also: Pacing System, Time Management Aid)

An assistive technology that helps individuals with cognitive impairments manage the timing and sequence of activities in daily routines. Pacing aids provide cues — visual, auditory, or tactile — to indicate whether the user is on schedule, ahead, or behind, without requiring…

Packet Loss(also: Network Packet Loss, Data Loss)

The failure of data packets to reach their destination during network transmission, common in VoIP and mobile telephony. Packet loss causes audio dropouts, distortion, and reduced intelligibility. Research shows that 20% packet loss can render voice telephony essentially…

Page Fragmentation(also: Visual Fragmentation, Content Fragmentation)

A web accessibility problem where different types of content on a web page (news articles, advertisements, navigation menus, related links) are visually grouped using colours, spacing, images, and layout but lack structural markup that would allow non-visual users to identify…

Page Landmarks(also: ARIA Landmarks, Landmark Regions, Landmark Roles)

Named regions of a web page that identify its high-level structure — for example banner, navigation, main, complementary, search, form, contentinfo — so that assistive technology can expose them as jump targets. Landmarks are typically declared with semantic HTML elements…

Page Linearization(also: Content Linearization, DOM Linearization, Source Order)

The process by which screen readers and other assistive technologies present web page content as a sequential, one-dimensional stream of text, typically following the order of elements in the HTML source code. Since web pages are designed as two-dimensional visual layouts where…

Page Magnification(also: Page Zoom, Web Page Magnification)

An accessibility feature that enlarges the entire visual presentation of a web page, including text, images, and layout elements, to make content easier to see for people with low vision or visual fatigue. Unlike text-only size increases, page magnification scales all page…

Page Sampling(also: Page Selection Strategy, Website Sampling)

The methodology used to select which pages within a website will be evaluated during an accessibility assessment. Common strategies include evaluating only the home page, testing specific page types (login, contact, sitemap), using hierarchical depth-based selection, or the…

Page Segmentation(also: Web Page Segmentation, VIPS)

The process of dividing a web page into distinct visual or structural blocks based on layout cues such as whitespace, borders, colors, and font properties. Page segmentation algorithms like Vision Based Page Segmentation (VIPS) analyze the rendered appearance of pages to…

Page Structure Preservation(also: Layout Preservation, Structure Retention)

The principle of maintaining the original spatial layout and DOM structure of a webpage when applying accessibility enhancements, content filtering, or other modifications. Preserving page structure ensures that users' mental models of familiar websites remain intact, that…

Page Turner(also: Page Turning Aid)

Any device, tool, or person that assists a musician in turning the pages of a music score during performance. Traditional page turners are human assistants who sit beside a musician and turn pages on cue. Technological alternatives include Bluetooth foot pedals for digital…

Pain Communication(also: pain expression, communicating pain)

The verbal and non-verbal processes through which a person conveys their pain experience to others, including family members, carers, and healthcare professionals. Chronic pain presents particular communication challenges because it is inherently subjective and invisible, often…

Pain Invalidation(also: chronic pain disbelief, pain dismissal)

The experience of having one's pain dismissed, disbelieved, or minimised by others, including healthcare professionals, family members, and social contacts. Pain invalidation is a pervasive barrier for people with chronic pain conditions, particularly primary pain syndromes such…

Pain Self-Management(also: chronic pain self-management)

A person-centred approach to living with chronic pain in which the individual takes an active role in managing their own condition through daily coping strategies, behavioural adaptations, and use of support resources, rather than relying solely on clinical interventions. Pain…

Pair Programming(also: Paired Programming, PP)

A software development practice where two programmers work together at one workstation, with one writing code (the "driver") and the other reviewing each line as it is typed (the "navigator" or "observer"). The two developers switch roles frequently. Pair programming promotes…

Palm Drawing(also: Palm Mapping, Palm Tracing)

A technique used by Orientation and Mobility (O&M) specialists to teach routes to people who are blind or have low vision. The instructor holds the person's palm face up and traces the path of a route with their finger while simultaneously providing verbal instructions. This…

Panel Transition Cue(also: Scene Transition Cue, Panel Change Signal)

An auditory signal used in audio-described comics and webtoons to indicate that the narrative has moved to a new panel, scene, or page. Panel transition cues help visually impaired listeners maintain orientation within the sequential narrative structure of comics, where visual…

Panning(also: Screen Panning, Viewport Panning)

The act of moving the visible area of a screen magnifier or viewport across a webpage or application to view content that extends beyond the currently displayed portion. For screen-magnifier users, panning is a fundamental but often arduous interaction technique, requiring…

Pantograph(also: Haptic Pantograph)

A haptic input device that allows users to explore a two-dimensional surface by physically moving a stylus or finger pad across an exploration area, while receiving tactile feedback from an attached tactile display. In accessibility applications, the pantograph enables people…

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

A rapid design technique that uses paper, cardboard, and other simple materials to create tangible representations of product concepts before investing in digital or electronic implementation. Paper prototyping allows designers and users to quickly explore form, layout, and…

Para Powerlifting(also: Adaptive Powerlifting, Paralympic Powerlifting)

A Paralympic strength sport in which athletes with physical disabilities perform bench press lifts. Unlike able-bodied powerlifting which includes squat, bench press, and deadlift, para powerlifting focuses solely on the bench press to accommodate athletes with lower limb…

Para-Athlete(also: Disabled Athlete, Adaptive Athlete)

An athlete with a disability who competes in adaptive or Paralympic sports. Para-athletes may have physical disabilities (amputations, spinal cord injuries, cerebral palsy), visual impairments, or intellectual disabilities. They compete using adaptive equipment such as…

Paradox of the Active User

The Paradox of the Active User, identified by Carroll and Rosson (1987), refers to the observation that computer users systematically avoid investing time in learning more efficient tools or methods, even when doing so would yield significant long-term productivity gains. Users…

Paralinguistic Cues(also: Paralanguage, Paralinguistic Features, Non-verbal Vocal Cues)

Aspects of spoken communication that carry meaning beyond the literal words themselves: tone of voice, pitch contour, loudness, rhythm, tempo, stress, pauses, and voice quality. Paralinguistic cues convey emotion, emphasis, sarcasm, uncertainty, speaker identity, and social…

Paralinguistic Features(also: Prosodic Cues, Non-Verbal Speech Features)

Aspects of spoken communication that convey meaning beyond the literal words, including pitch, loudness, rhythm, tone, and emotional affect. These features are critical for understanding speaker intent, sarcasm, emphasis, and emotional state but are typically lost in standard…

Parallax(also: Visual Parallax, Binocular Parallax)

Parallax is the apparent displacement or difference in position of an object when viewed from two different vantage points. In human vision, binocular parallax — the slight difference between the images seen by each eye due to their spatial separation — is a primary cue for…

Parallel Play(also: Parallel Activity)

A form of social interaction where individuals engage in separate activities alongside each other without direct interaction. Originally described in child development research by Mildred Parten in 1932, parallel play has been recognized in neurodivergent communities as a…

Parallel Viewing(also: Dual-Screen Viewing)

A media consumption strategy in which viewers use a second screen alongside the primary display to access supplementary information, accessibility features, or alternative content representations without interrupting the main viewing experience. For people with disabilities,…

Paralympic(also: Paralympic Games, Paralympics)

The international multi-sport event for athletes with physical, visual, and intellectual disabilities, organized in parallel with the Olympic Games. The first organized Paralympic Games took place in 1948, with official recognition beginning in 1960. The Paralympic movement…

Paralysis(also: Paralyzed, Paresis)

The partial or complete loss of voluntary muscle function, resulting from damage to the motor nervous system. Common causes include spinal cord injury, stroke, traumatic brain injury, motor neuron diseases such as ALS, multiple sclerosis, cerebral palsy, and brainstem lesions…

Parameter Mapping Sonification(also: Parameter Mapping, Auditory Parameter Mapping)

A sonification technique that represents changes in data dimensions through corresponding changes in auditory dimensions such as pitch, loudness, timbre, spatial position (panning), tempo, or reverberation. Unlike auditory icons (which use recognizable real-world sounds) or…