Velocity

Part of speech: noun

Pronunciation: /vəˈlɒsəti/

Definitions

1. The rate at which an object changes its position in a specific direction over time
2. The measurement of an object's speed combined with its direction of travel, signifying its movement through space over time
3. The speed of an object in a specified direction, indicating how fast it is moving along with the path it follows

Etymology: The Latin root "vēlōx" meant "swift" or "fast," and it gave English a word that now sits in physics classrooms rather than on racetracks. "Velocity" came into English by way of Middle French "vélocité," which in turn borrowed the Latin noun "vēlōcitās," meaning "speed." Its sibling is "veloce," the Italian musical instruction for playing quickly, which entered English as a doublet of the same Latin source. The notable thing is how narrow the modern sense became. In everyday speech "velocity" once simply meant rapidity, much like "speed," and the two were close synonyms. Physics later gave it a precise meaning: speed together with direction. That added directional component is what separates velocity from speed in a textbook, so a car circling a track has constant speed but changing velocity, because its direction keeps changing.

Synonyms: speed, swiftness, rapidity

Antonyms: slowness, sluggishness