extremely rare; mostly used in specialist or historical contexts
Grammar Patterns
usually singular
Common Mistakes
He rode a unicycle with two wheels.
He rode a unicycle with one wheel.
A unicycle has only one wheel by definition; do not confuse it with a bicycle.
Word family
unicyclist
nounB2
Synonym discussion
Sense: noun/1
All four words refer to pedal-powered vehicles, but they differ in the number of wheels. A unicycle has one wheel, a bicycle has two, and a tricycle has three (tripods are more stable, making tricycles common for young children). Monocycle is a very rare synonym for unicycle, mostly encountered in engineering or historical writing — in everyday English, unicycle is the only word people use. If you say 'I rode my bicycle to work,' listeners expect two wheels; if you say 'I rode my unicycle to work,' they will picture a single wheel under you and probably ask for a story.
Unicycle was coined in the late 1800s by blending uni- (from Latin unus, meaning 'one') and cycle (from Greek kyklos, meaning 'circle' or 'wheel'), modelled on the word bicycle. The name simply means 'one-wheeled vehicle'.