A wheelchair is a device used for mobility by people for whom walking is difficult or impossible, due to illness or disability.
It typically consists of a seat 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. The 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 racing.
Adapting the built environment to make it more accessible to wheelchair users is one of the key campaigns of disability rights movements. (See, for example, ultra low floor trams and buses.)
