A Segway is a two-wheeled, self-balancing personal transporter device invented by Dean Kamen. It is a registered trademark of Segway Inc. It was brought to market in 2001 as the Segway HT, and then subsequently as the Segway PT. HT is an initialism for "human transporter" and PT for "personal transporter."

A dicycle is a vehicle with two parallel wheels, side by side, unlike single-track vehicles such as motorcycles and bicycles, which have two wheels inline. Originally used to refer to devices with large wheels and pedals, the term is now used in relation to powered self-balancing scooters with smaller wheels and no pedals such as the Segway PT and the self-balancing hoverboard.