A wheelchair is a device used for mobility by people for whom walking is difficult or impossible, due to illness or disability.
- a wheelchair human-powered by the rider (alternatively it can be pushed by another person).
- an electric wheelchair
- a wheelchair that can only be pushed by another person (also known as a transport chair, having all four wheels of equal size, usually approximately 8 inches in diameter, instead of two large in the rear [usually approximately 22 -24 inches] and two small 8 inch wheels in the front. )
It typically consists of a seat and back supported on two large wheels on an axle attached towards the back of the seat and two small wheels near the feet, though there are often small additional features to prevent toppling or to assist mounting curbs. Wheelchairs come in many sizes and colors and can be highly customized with several options including seat size (width and depth), seat to floor height, footrests/legrests, and much more.
A person moves by pushing with his/her hands circular bars on the outside of the large wheels with a diameter that is slightly less than that of the wheels, or by actuating motors, usually with a joystick.
Experiments have also been made with unusual variant wheels, like the omniwheel or the mecanum wheel . These allow more directional movement options.
Disabled athletes use streamlined sport wheelchairs for sports that require speed and agility, such as basketball, rugby, tennis and racing.
Powerchairs are extremely maneuverable because they are controlled with a joystick device that one can operate with as little as one finger. Powerchairs are ideal for navigating tight spaces indoors and can often turn 360 degrees in the same spot. They can easily be customized to accommodate the rider's specific situation. They can be used as part of adapted sports such as Wheelchair Soccer.
Adapting the built environment to make it more accessible to people with disabilities who use wheelchairs is one of the key campaigns of disability rights movements and the Americans with Disabilities Act of 1990 (ADA). For example, the construction of low floor trams and buses is being encouraged whereas the use of paternosters in public buildings without any alternative method of transportation has been criticized due to the lack of access for wheelchair users. Modern street furniture design now incorporates better accessiblity for people with disabilities.