Glossary

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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,…

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