A tricycle — a cycle with three wheels. It is the short, friendly, spoken form, the way bike is short for bicycle. Most often it means a small child's first riding toy, with pedals on the front wheel, before they are steady enough for a two-wheeler. But it also covers grown-up machines: a three-wheeled motorbike, or the low three-wheeled cycle an older person or a person with balance problems rides because it cannot fall over.

Because it is a shortening, it feels casual and warm. Parents say trike; a shop catalogue might write tricycle. You will also hear it as a verb in some places — to trike somewhere is to travel by trike — but that is uncommon and you never need to produce it. In the Philippines, tricycle (a motorbike with a side car) is a normal way to get around town, and English speakers there use it constantly; that is worth knowing if you travel.

Also note: dinosaur fans call Triceratops a trike too, though that is a nickname, not the dictionary word.