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Velocity

vuh-LOSS-ih-tee /vəˈlɒsɪti/

nounB2GRESAT

technicalformal

The speed of something in a given direction.

Unlike 'speed' (a scalar quantity), 'velocity' is a vector quantity, meaning it has both magnitude (how fast) and direction (where to). For example, 60 mph is a speed, but 60 mph north is a velocity.

The story behind the word. The word 'Velocity' comes from the Latin 'velocitas', meaning 'swiftness' or 'speed'. This, in turn, is derived from 'velox', meaning 'swift' or 'rapid'. While 'speed' has been in English for much longer, 'velocity' gained its specific scientific meaning, emphasizing direction, in the 17th century, especially with the rise of classical mechanics.

Word relationships

speed: Speed is the rate of movement without regard to direction; velocity includes direction.
pace: Pace often refers to a rate of progress or a particular speed, but usually lacks the directional component of velocity.

stillness: A state of no motion, therefore zero velocity.
rest: A state of not moving.

Commonly confused with

Acceleration: Velocity is speed with direction; acceleration is the rate of change of velocity.

Word family

velocimeter (noun): an instrument for measuring velocity

Collocations

constant velocity
terminal velocity
angular velocity
initial velocity
escape velocity

Example sentences

"The projectile's initial velocity was 100 meters per second upwards." In a physics problem.
"Although its speed is constant, a satellite in orbit constantly changes its velocity because its direction of motion is always changing." Describing planetary movement.
"Engineers must calculate the fluid velocity through the pipes to ensure efficient flow and prevent blockages." In engineering.

Memory hook

Think of a 'VELO' bike race. You need to know not just how fast, but in which 'VELO' (direction) you're going. Speed + Direction

When not to use

In casual conversation, 'speed' is often perfectly adequate. Use 'velocity' when the direction of movement is relevant or when precision in a scientific context is required.

Fun facts

The speed of light in a vacuum is approximately 299,792,458 meters per second, often denoted as 'c'.
The concept of velocity is crucial in understanding orbital mechanics and projectile motion.