What is the term for a bicycle with three wheels?

A bicycle with three wheels is called a tricycle.

The word describes a broad family of human-powered vehicles arranged in several ways. A delta tricycle has two wheels at the rear and one steering wheel at the front, while a tadpole tricycle has two front wheels and one rear wheel. Recumbent, cargo, hand-powered and cycle-rickshaw designs are also tricycles.

Tricycles have existed since the 17th century; Stephan Farffler is often credited with an early hand-powered example from around 1655 or 1680. Their three-wheel layout offers stability at rest, making them popular with children, older riders and people who find balancing a two-wheel bicycle difficult.

A common mix-up is assuming that three wheels always make a tricycle safer in every situation. Conventional upright tricycles can tip during fast turns because their frames do not lean like bicycles. Modern tilting or low-slung recumbent designs address some of that limitation. “Trike” is the familiar shortened form.