Glossary

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Ambiguous keyboard(also: T9 input, Multi-tap disambiguation)

A text entry method in which multiple letters are mapped to each physical key, requiring disambiguation algorithms (typically dictionary-based) to determine the intended word from the sequence of key presses. Originally popularized by T9 predictive text on mobile phone numeric…

Braille Input(also: Braille Keyboard Input, Braille Screen Input)

A text entry method that allows users to type characters using Braille code on a device, rather than a standard QWERTY keyboard. On touchscreen devices, Braille input typically maps finger taps or gestures to the six dots of a Braille cell, enabling blind users who know Braille…

Continuous Motion Input(also: Gesture Typing, Swipe Input)

A text entry method where the user traces a continuous path across an on-screen keyboard, passing through the desired letters or keys without lifting their finger. This approach can be faster than discrete tapping and is particularly beneficial for users with motor impairments…

Dasher

A zooming text entry interface in which users write by navigating through a world of nested boxes, each labeled with a letter and sized proportionally to its probability under a language model. Users control navigation using any pointing device, including eye trackers, mice, or…

Decision Delay(also: Cognitive Delay, Selection Delay)

The time a user spends deciding whether to accept or reject a suggestion from a predictive system, such as a word prediction list on an assistive technology device or keyboard. Decision delay is a cognitive cost that can offset the motor efficiency gains of word prediction:…

EdgeWrite(also: Edge Write)

A gestural text entry method that uses the physical edges and corners of a square input area to guide character formation. Unlike traditional handwriting recognition that analyzes the full path of a stroke, EdgeWrite recognizes characters based on the sequence of corners hit,…

Gaze Typing(also: Eye Typing, Gaze-Based Text Entry, Eye-Typing)

A text input method that uses eye tracking technology to allow users to type by looking at keys on a virtual on-screen keyboard. The most common technique is dwell-based selection, where the user fixates on a letter for a set duration (typically 300-1000 milliseconds) to select…

Gesture Typing(also: Swipe Typing, Trace Typing, Glide Typing)

A text entry method on touchscreen devices where the user enters a word by continuously gliding their finger from letter to letter on a virtual keyboard without lifting it, rather than tapping each key individually. The continuous trace is interpreted by a statistical decoder…

Keypad(also: Numeric Keypad, Phone Keypad, Small Keypad)

A keypad is a compact input device with a small number of keys, typically arranged in a 3x4 grid (phone keypads) or other constrained layouts. In accessibility contexts, keypads are relevant both as the *only* viable input device for some users — small physical keypads are…

Keystroke Saving(also: KS, Keystroke Reduction)

A metric used to evaluate word prediction and word completion systems, measuring the percentage of keystrokes that a user can avoid by accepting system predictions instead of typing each character individually. Keystroke saving is calculated by comparing the number of keystrokes…

Keystroke Savings(also: KS, Key Savings)

A metric used to evaluate word prediction systems, measuring the percentage of keystrokes eliminated by accepting predictions compared to typing the full text character by character. While keystroke savings is commonly reported in AAC research, it does not directly translate to…

Keystrokes Per Character(also: KSPC)

A metric used to evaluate the efficiency of text-entry methods by measuring the average number of keystrokes required to produce each character of text. A lower KSPC indicates a more efficient input method. For standard MultiTap on a 12-key phone keypad, the theoretical best…

Minimum String Distance(also: MSD, Edit Distance, Levenshtein Distance)

A metric for measuring text entry accuracy by calculating the minimum number of single-character insertions, deletions, and substitutions needed to transform the transcribed text into the intended text. In text entry research, the MSD error rate is typically expressed as a…

MultiTap(also: Multi-Tap)

A standard text-entry method used on mobile phone keypads where groups of three or four letters are assigned to each numeric key, and users press the key consecutively to cycle through the available letters. For example, pressing the "2" key once produces "a," twice produces…

NavTap

A navigational text-entry method designed for blind mobile phone users that reduces the cognitive load associated with inputting text without visual feedback. NavTap organizes the alphabet into five rows beginning with vowels and allows users to navigate between letters using…

Nomadic Text Entry(also: Mobile Text Entry, On-the-Go Texting)

The practice of inputting text on a mobile device while moving through or actively engaging with the physical environment, as opposed to typing while stationary. For people who are blind or visually impaired, nomadic text entry presents unique challenges because it requires…

Predictive Disambiguation(also: Dictionary-based Predictive Disambiguation, DBPD, Word Disambiguation)

Predictive disambiguation is the class of text-entry techniques in which each user input event is intentionally ambiguous (one keystroke covers several possible letters, one swipe covers many possible paths) and software resolves the ambiguity into a most-likely word using a…

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,…

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…

Switch Keyboard(also: Scanning Keyboard, On-Screen Scanning Keyboard)

A switch keyboard is a virtual keyboard interface designed for people with severe motor disabilities who cannot use a standard keyboard or pointing device. It works through a scanning mechanism: a cursor automatically moves across rows and columns of the keyboard, and the user…

T9(also: Text on 9 Keys, Tegic T9)

T9 (Text on 9 Keys) is a dictionary-based predictive text-entry method developed by Tegic Communications in the 1990s for mobile phone keypads with multiple letters assigned to each numeric key. Rather than pressing a key multiple times to cycle through letters (the older…

Text Entry Rate(also: Typing Speed, Characters Per Minute, CPM)

A measure of how quickly a user can input text using a given method, typically expressed in words per minute (WPM) or characters per minute (CPM). One word is conventionally defined as five characters including spaces. For standard QWERTY keyboards, professional typists achieve…

Text Generation Rate(also: TGR, Text Entry Rate, Text Entry Speed)

The speed at which a user produces text, typically measured in words per minute (WPM) or characters per second. Text generation rate is a key performance metric in assistive technology evaluation because it captures the overall efficiency of a text entry system, accounting for…

Textonym(also: T9 Ambiguity)

Words that share the same sequence of key presses on a telephone-style number pad, such as "bat" and "cat" which both map to the key sequence 2-2-8. Textonyms are a significant design consideration in AAC and text entry systems that use reduced keyboard layouts, as the system…

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