Glossary

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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…

Tetraplegia(also: Quadriplegia)

A condition resulting from injury to the cervical (neck) portion of the spinal cord, causing partial or complete loss of motor function and sensation in all four limbs as well as the trunk. The extent of impairment varies depending on the level and completeness of the injury,…

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 target(also: Tap target, Touch target size, Target size)

The interactive area on a touchscreen or pen-based display that responds to user input when tapped or pressed. Touch target size is a critical accessibility consideration because targets that are too small or too closely spaced cause selection errors, particularly for older…

Trackball

A trackball is a pointing device consisting of a ball housed in a stationary socket that the user rotates to move the on-screen cursor, with buttons nearby for clicking. Unlike a mouse, a trackball does not require arm movement across a surface, making it valuable for people…

Tremor(also: Hand Tremor, Essential Tremor)

An involuntary, rhythmic shaking movement of one or more parts of the body, most commonly affecting the hands. Tremor can result from various conditions including essential tremor, Parkinson's disease, multiple sclerosis, stroke, or medication side effects, and its severity can…

Upper Body Motor Impairment(also: Upper Limb Impairment, Upper Extremity Disability)

A condition affecting the motor function of the arms, hands, or upper body that limits or prevents the use of standard input devices such as keyboards, mice, and touchscreens. Upper body motor impairments can result from conditions including amputation, cerebral palsy, spinal…

Variable Pointing Performance(also: Variable Pointing Ability, Intermittent Pointing Difficulty)

A condition where a person's ability to accurately use a pointing device (such as a mouse, trackpad, or touchscreen) fluctuates over time due to factors like physical impairments, fatigue, medication effects, aging, or environmental conditions. Unlike permanent severe motor…

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

A software-rendered keyboard displayed on screen that allows users to input text by clicking, tapping, or hovering over virtual keys using a mouse, trackball, touchscreen, eye tracker, or other pointing device. Virtual keyboards are essential assistive technology for people with…

Vocal Programming(also: Voice Coding, Speech-Based Programming, Voice Programming)

The practice of writing, editing, and navigating computer code using speech recognition rather than keyboard input. Vocal programming is an important accessibility concern because conventional software development tools implicitly require the use of a keyboard, creating a…

Zoom Interface(also: Zoom Screen, Zoomable User Interface, ZUI)

A user interface technique that allows users to magnify a portion of the screen to increase the effective size of interface elements, making them easier to select with low-precision pointing devices such as eye trackers or head mice. Unlike simple screen magnification for low…