Glossary

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Motor Imagery(also: MI, Mental Practice, Imagined Movement)

The mental rehearsal or imagination of physical movement without actual motor execution. In brain-computer interfaces, motor imagery typically involves imagining left-hand or right-hand movements, which produce distinct patterns in the sensorimotor cortex that can be detected…

Mouse(also: Computer Mouse, Optical Mouse)

A mouse is a hand-operated pointing device that translates relative motion across a flat surface into movement of an on-screen cursor, with one or more buttons and usually a scroll wheel for selection and additional commands. It is the dominant pointing device for desktop…

Mouse Pointer(also: Cursor, Screen Pointer, Onscreen Pointer)

The small graphical indicator on a computer screen that represents the position of a pointing device such as a mouse, trackpad, or stylus. The mouse pointer is used to identify and interact with interface elements in graphical user interfaces through pointing, clicking, and…

Mouth Interface(also: Mouth-operated interface, Mouth-based input)

An input modality that uses mouth movements - tongue position, cheek puffs, jaw motion, lip gestures, breath, or sip-and-puff - to control a computer, wheelchair, or XR system. Mouth interfaces serve people with limited upper-limb mobility (e.g., spinal cord injury, muscular…

Multimodal Input(also: Multimodal Interaction, Multi-modal Input)

An interaction approach that allows users to communicate with computing devices or systems through multiple input channels — such as touch, voice, eye gaze, head movement, facial expressions, hand gestures, brain-computer interfaces, and biometrics — either simultaneously or…

Multimodal Text Editing(also: Multimodal Editing)

A text editing approach that combines multiple input modalities—such as gestures, voice commands, and touch—to enable more efficient and accessible text correction. For users with disabilities, multimodal editing can reduce reliance on any single input method, allowing each…

Multitouch Surface(also: Multi-Touch Interface, Multitouch Interface, MTS)

A multitouch surface is an input device that uses optical or capacitive sensors to detect and track multiple simultaneous finger contacts on a flat surface. Unlike conventional touchpads that rely on a single finger for functionality, multitouch surfaces can recognize complex…

Occlusion(also: Hand Occlusion, Finger Occlusion, Visual Occlusion)

In the context of touchscreen and pen-based interaction, occlusion refers to the user's hand or finger blocking their view of content on the screen while interacting with it. Occlusion is a significant accessibility barrier, particularly for older adults and users with motor…

On-body Input(also: Skin-based Input, Body-based Interaction)

An interaction technique that uses the surface of the user's own body — typically the hand, arm, or other skin areas — as an input surface for controlling digital devices. On-body input is sensed through wearable cameras, depth sensors, capacitive touch sensors, or acoustic…

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…

Pen Input(also: Stylus Input, Pen-Based Input)

An input method using a pen or stylus to interact with a computing device, typically through direct manipulation on a touchscreen or digitizer. Pen input offers advantages for users with certain motor impairments: compared to mice, pens allow users to leverage hand-eye…

Perceptual User Interface(also: PUI, Natural User Interface)

A human-computer interaction paradigm that uses natural human capabilities such as vision, speech, gestures, and body movement as input modalities rather than relying on traditional devices like keyboards and mice. Perceptual user interfaces leverage sensors and computer vision…

Point-and-Click(also: Point and Click, Click Target)

A fundamental interaction paradigm in graphical user interfaces where the user moves a cursor to a target on screen and activates it by pressing a button on a pointing device such as a mouse or trackpad. Point-and-click tasks are central to GUI-based computing but present…

Pointer Speed(also: Mouse Gain, Cursor Speed, Mouse Speed)

An operating system setting that controls how far the cursor moves on screen relative to physical movement of the mouse or pointing device. Higher pointer speed (gain) means less physical movement is required to traverse the screen, while lower speed provides finer control but…

Pointing(also: Pointing Performance, Mouse Pointing, Cursor Pointing)

The act of moving a cursor or pointer to indicate a specific location on screen, typically to select, activate, or interact with an interface element. Pointing is a fundamental computer interaction that can be challenging for individuals with motor impairments, tremors, limited…

Pointing Task(also: Target Acquisition Task, Fitts' Task)

A fundamental human-computer interaction task in which users move a cursor (via mouse, touchpad, finger, or other input device) to click or tap on a target. Pointing tasks are governed by Fitts' Law, which predicts that movement time increases with distance to the target and…

Predictive Text(also: Text Prediction, Word Prediction, Autocomplete)

A software feature that suggests words or phrases as the user types, based on context, language models, and the user's typing history. Predictive text is a significant accessibility feature for people with motor impairments because it reduces the number of keystrokes needed,…

Push-to-Talk(also: PTT, Push to talk)

An interaction pattern where a user presses and holds (or taps) a dedicated button to signal the start of an input — historically used in two-way radios, now common in voice assistants and conversational interfaces as an alternative to continuous listening. In accessibility…

QWERTY Keyboard(also: QWERTY)

A QWERTY keyboard is the dominant Latin-script keyboard layout, named for the first six letters on the top row, originally designed for mechanical typewriters and carried forward into computers and mobile devices. On mobile handsets, QWERTY has appeared in both hardware form…

Redundant Input(also: Redundant Input Channels, Multimodal Redundancy)

A design approach in which a user interface accepts the same command through more than one input channel — for example, voice and gesture, keyboard and pointer, or speech and switch — so that users can choose whichever modality suits their current abilities, context, or…

Row-Column Scanning(also: RCS, Grid Scanning, Two-Switch Scanning)

The most widely used single-switch selection method for augmentative and alternative communication (AAC) devices and on-screen keyboards. Options are arranged in a two-dimensional grid, and the interface sequentially highlights each row. When the user clicks their switch, the…

Scanning(also: Switch Scanning, Sequential Scanning)

An input method used in augmentative and alternative communication (AAC) that allows users with severe motor impairments to make selections using one or more switches. The system sequentially highlights items in a vocabulary set, and the user activates a switch when the desired…

Scanning Delay(also: Tscan, Scan Rate, Dwell Time)

The time interval a scanning system waits before automatically advancing to highlight the next item. Setting scanning delay appropriately is critical for switch access users: too short causes selection errors because the user cannot respond quickly enough; too long dramatically…

Scanning System(also: Automatic Scanning, Group Scanning, Row-Column Scanning)

An assistive technology input method in which selectable items are sequentially highlighted on screen, and the user activates a switch (or other simple input) when the desired item is highlighted. Scanning systems are designed for people with severe motor disabilities who can…

Screen-Free Editing(also: Screenless Editing, Eyes-Free Editing)

Text editing that does not require visual interaction with or physical contact with a device screen. Screen-free editing approaches use alternative input methods such as mid-air gestures, voice commands, or wearable device controls to manipulate text. This is particularly…

Screenless Interaction(also: Screen-Free Interaction, Displayless Interaction)

Interaction with digital systems that does not require a visual display, enabling users to operate devices while untethered from screens. For people who are blind, screenless interaction eliminates the need to hold and touch a phone screen to find visual affordances they cannot…

Segmentation Problem(also: Stroke Segmentation, Input Segmentation, Gesture Segmentation)

The segmentation problem in text entry and gesture recognition refers to the challenge of determining where one input unit (such as a letter, word, or gesture) ends and the next begins when there is no explicit delimiter between successive inputs. For stylus-based systems,…

Selection Keyboard(also: On-Screen Keyboard, Scanning Keyboard, Virtual Keyboard)

A text entry interface where characters are displayed in a grid on screen and users select them by navigating a cursor or highlight to the desired character using an alternative input device such as a joystick, switch, or eye tracker. Selection keyboards are commonly used by…

Single-Switch Access(also: One-switch access, Single switch scanning)

An input method that allows users to control a computer, AAC device, or other technology using only one switch or button. Users with severe motor impairments who cannot operate a keyboard, mouse, or touchscreen can use various switch types—including buttons pressed by hand,…

Sip-and-Puff(also: Sip and Puff Switch, Pneumatic Switch)

An assistive technology input device that detects air pressure changes from a user sipping (inhaling) or puffing (exhaling) through a straw or tube to generate control signals. Sip-and-puff systems are primarily used by people with severe motor impairments, particularly those…

Smart Ring(also: Ring-Form Wearable)

A wearable computing device worn on a finger, typically combining sensors (motion, biometric, or camera) and/or actuators (vibration, kinesthetic feedback) in a ring form factor. In accessibility, smart rings have been proposed as discreet input devices, vibrotactile navigation…

Smartwatch Interaction(also: Watch-Based Interaction)

The methods and techniques used to interact with smartwatch devices, including touch gestures on the small screen, physical button and crown inputs, and motion-based gestures detected by onboard sensors. Smartwatches present unique interaction challenges due to their small form…

Soft Keyboard(also: On-screen Keyboard, Virtual Keyboard, OSK)

A keyboard displayed on a screen that is operated by a pointing device (mouse, touch, head tracker, eye gaze, or switch) rather than physical key presses. Soft keyboards are essential assistive technology for people who cannot use a standard physical keyboard due to motor…

Speech Input(also: Voice input, Voice control, Speech recognition input)

An input method that allows users to control devices or enter text by speaking rather than using manual touch or keyboard input. Speech input is particularly important for people with visual impairments, who use it significantly more often than sighted users to overcome the…

Steady Tapping

The ability to place a finger on a touchscreen target and hold it still long enough for the system to register a deliberate tap, as opposed to the unintentional movements caused by hand tremor. For users with motor impairments, maintaining a steady tap is a significant challenge…

Stenotype(also: Stenography, Shorthand Typing, Machine Shorthand)

A specialised text-entry method that uses a keyboard with fewer keys than a standard QWERTY layout, where multiple keys are pressed simultaneously (chording) to represent phonetic sounds, syllables, or entire words. Stenotype enables trained operators to achieve speeds of…

Sticky Keys(also: Sequential Key Entry)

An operating system accessibility feature that allows users to press modifier keys (Shift, Ctrl, Alt, Command) sequentially rather than simultaneously, making keyboard shortcuts accessible to people who can only press one key at a time. Sticky Keys is built into Windows, macOS,…

Subvocal Input(also: Subvocal Control, Subvocalisation Input)

An input method that uses very quiet or nearly silent vocalisations — sounds produced with minimal vocal effort that are typically inaudible to nearby people. Subvocal input includes techniques such as humming, whispering, or producing sounds detectable only by bone-conduction…

Switch Access(also: Switch Control, Switch Scanning)

A method of computer and device interaction that uses one or more switches as input devices, designed for people who cannot use standard keyboards, mice, or touchscreens due to motor impairments. Switch access is built into major operating systems (iOS Switch Control, Android…

Switch Scanning(also: Scanning Mode, Auto Scanning)

An input method for assistive technology where options are sequentially highlighted (scanned) and the user activates a single switch to select the currently highlighted item. This enables people with severe motor disabilities to access computers, communication devices, and other…

Symbrachydactyly

A rare congenital condition in which a child is born with abnormally short fingers that may be webbed, misshapen, or missing. The name combines "sym" (joined), "brachy" (short), and "dactyly" (finger). Typically only one hand is affected, and the underlying bone, muscle,…

Target-Based Navigation(also: Target-Based Cursor Control, Object-Based Navigation)

A cursor control method where users identify the desired destination directly by name or label, such as saying "Select Friday" to move the cursor to that word on screen. Target-based navigation can be efficient when targets are clearly identifiable, but becomes error-prone as…

Text Entry(also: Text Input, Text Generation)

The process of entering text into a computer or communication device, encompassing the full range of input methods from standard keyboards to alternative approaches used in assistive technology such as on-screen keyboards, word prediction, scanning, switch-based input, eye…

Throughput(also: Throughput (Fitts), Pointing Throughput)

In human-computer interaction, throughput is a combined speed-accuracy metric derived from Fitts's law that measures the efficiency of aimed pointing movements, expressed in bits per second (bps). It is calculated by dividing the index of difficulty (a function of target…

Touch Accessibility(also: Touchscreen Accessibility)

The design and adaptation of touch-based interfaces to be usable by people with diverse motor, sensory, and cognitive abilities. Touch accessibility addresses challenges including insufficient target sizes for users with limited fine motor control, lack of alternatives to…

Touch Drift(also: Finger Drift)

The displacement of a finger's contact point on a touchscreen between the initial finger-down position and the final finger-up position during a single touch interaction. Touch drift measures how far a touch "slides" from where it started to where it ended, distinct from touch…

Touch Panel(also: Touch Tablet, Touch-Sensitive Panel, Digitizer Tablet)

A flat, pressure-sensitive input surface that detects the position of a finger or stylus when it makes contact. Unlike touchscreens, which combine display and input on the same surface, a touch panel is a separate input device placed over or alongside a display. In…

Touch-Free Interaction(also: Contactless Interaction, No-Touch Interface)

Interaction with digital systems without physically touching any device surface, achieved through gestures, voice, eye tracking, brain-computer interfaces, or proximity sensors. Touch-free interaction is important for accessibility because touchscreens present significant…

Touchpad(also: Touch Tablet, Touch-Sensitive Pad)

A flat, pressure-sensitive input device that detects the position of a finger or stylus on its surface. In assistive technology contexts, touchpads are used as interactive overlays for tactile graphics and maps, enabling users who are blind to place a tactile printout on the pad…

Touchpad Navigation(also: Trackpad Navigation)

A method of interacting with digital content by dragging fingers or pressing specific positions on a smooth-surface touchpad input device. In accessibility contexts, touchpad navigation enables direct manipulation of spatial interfaces — such as maps or diagrams — by mapping…