A sliding door is a type of door that is mounted on or suspended from a track for the door to slide, usually horizontally and outside. It is a feature predominantly found in minibuses, buses, and vans, so as to allow a large unobstructed access to the interior for loading and unloading of passengers or cargo without the doors interfering with adjacent space.

A suicide door is an automobile door hinged at its rear rather than the front. Such doors were originally used on horse-drawn carriages, but are rarely found on modern vehicles, primarily because they are less safe than a front-hinged door. Being rear-hinged, if the vehicle was moving and the door opened, aerodynamic drag would force the door open, and the driver/passenger would have to lean forward and out of the vehicle to close it. As seat belts were not in common use at that time, the risk of falling out of the car and into traffic was high, hence the name "suicide door".. Another reason could have been that while a door was open on a city street, a speeding car moving in the same direction as the parked car could rip a front-hinged door off the parked car but someone in side the adjacent seat, even if moving to leave the car, could not get scratched. However, with a suicide door, someone inside or partially outside the passenger compartment would get struck by the suicide door forcefully swinging back to a shut position due to the impact of the speeding car.