noun

rapidity

ruh-PID-uh-tee/rəˈpɪdəti/

The speed at which something happens or moves.

The cheetah's rapidity sends dust streaming behind its extended body.

A cheetah in full-speed pursuit of a small windblown tuft of dust, shown in an unmistakable airborne sprint with its body extended and dust streaming behind its paws.

Etymology

The ending turns “swift” into the quality of swiftness. Rapidity thus names speed itself, whether in physical motion or in how quickly an action or event happens.

In context

Kings and Generals206:09

Against Vendôme’s and Burgundy’s expectations, the Allies moved with surprising speed and rapidity.

War of the Spanish Succession: All Battles and Events - FULL DOCUMENTARY

More examples

Doctors are surprised by the rapidity of her recovery.
The current carries the boat downstream with alarming rapidity.
News travels with astonishing rapidity in our small town.

Forms

rapid adjective — Quick in movement, action, or change.

rapidly adverb — At a high speed or rate.

Similar words

speed: More neutral; can describe either fast or slow rates.
swiftness: Emphasizes quick movement or action rather than a measured rate.
quickness: Often emphasizes acting or responding without delay.