A fleet is a group of ships, airplanes, or vehicles operating together under one organization. A country's navy has a fleet of warships that patrol the oceans and protect its waters. Airlines own fleets of passenger jets that fly routes around the world. A delivery company might operate a fleet of trucks that bring packages to homes and businesses.

The word originally referred to ships, and throughout history, powerful nations built large fleets to explore, trade, and defend themselves. The Spanish Armada was a famous fleet of warships that sailed against England in 1588. Today, we still talk about naval fleets, but the word has expanded: a school district might have a fleet of buses, or a taxi company might maintain a fleet of cars.

As an adjective, fleet can also mean fast and nimble. A fleet-footed runner moves with quick, light steps. You might describe a deer as fleet because it darts through the forest with speed and grace. While this meaning is less common today, you'll still encounter it in books and poetry describing swift movement.